Examkin

Conventions of Punctuation

374 questions

All types374Multiple choice326Fill in the blank48
Question 221Question →

The conservator examined the ancient medieval manuscript under ultraviolet light; she discovered hidden layers of text that had been scraped away centuries ago.

Which choice represents the most effective punctuation for the underlined portion of the sentence?

Show answer & explanation

Answer: NO CHANGE

Answer

NO CHANGE
The correct option correctly uses a semicolon to separate two closely related independent clauses. Since both parts of the sentence have their own subjects and verbs and form complete thoughts, a semicolon is a grammatically correct way to link them without adding a coordinating conjunction.

Step-by-Step Solution

1
Analyze the grammatical structure of the clauses before and after the punctuation mark.
The clause before ('The conservator examined the ancient medieval manuscript under ultraviolet light') and the clause after ('she discovered hidden layers of text that had been scraped away centuries ago') are both independent clauses.
Each clause contains a subject and a verb and can stand alone as a complete sentence.
2
Determine the acceptable methods for joining two independent clauses.
Two independent clauses can be joined by either a semicolon alone, or a comma followed by a coordinating conjunction (such as 'and').
A semicolon is used here because there is no coordinating conjunction joining the two related, complete thoughts.

Key Concept

Semicolons are used to link two independent clauses that are closely related in thought when no coordinating conjunction is present.
Question 222Question →

The following passage is an excerpt from a science article about deep-sea marine biology.

Deep-ocean hydrothermal vents support thriving ecosystems in some of the most hostile environments on Earth. Organisms living near these vents—such as the giant tube worm, which lacks a mouth and digestive tract, rely on symbiotic bacteria for survival. These bacteria convert toxic chemicals from the vents into usable energy.

Which choice is the best replacement for the underlined portion of the sentence?

Show answer & explanation

Answer: tract—rely

Answer

The correct choice is the option that replaces the underlined text with 'tract—rely', using a dash to match the opening dash and properly close the nonessential phrase.
The sentence contains a nonessential parenthetical phrase ('such as the giant tube worm, which lacks a mouth and digestive tract') that is introduced by a dash. To maintain punctuation consistency, the phrase must also close with a dash. The correct choice provides this closing dash, properly separating the parenthetical information from the main verb 'rely'.

Step-by-Step Solution

1
Identify the nonessential parenthetical phrase within the sentence.
The phrase is 'such as the giant tube worm, which lacks a mouth and digestive tract'.
Determining where the parenthetical information begins and ends helps identify the punctuation needed to set it off.
2
Locate the punctuation mark used to introduce the parenthetical phrase.
A dash is used right before the phrase ('vents—such').
Standard punctuation rules require that parenthetical elements be set off by matching punctuation marks: either two commas or two dashes.
3
Evaluate the choices to find the punctuation mark that matches the opening dash.
A closing dash ('tract—rely') is required to maintain consistency and correctly connect the subject to the main verb.
Using a comma, semicolon, or period disrupts the sentence structure and violates punctuation consistency rules.

Key Concept

Punctuation consistency with parenthetical dashes
Question 223Question →

Because the regional agricultural board wanted to protect local crops from the unpredictable, destructive, insect pests, they recommended a combination of biological controls and crop rotation.

Which of the following choices best punctuates the underlined portion of the sentence?

Show answer & explanation

Answer: unpredictable, destructive insect pests, they recommended

Answer

The correct option is the one that reads 'unpredictable, destructive insect pests, they recommended'. This choice correctly punctuates the coordinate adjectives and sets off the introductory clause.
The correct choice properly identifies that 'unpredictable' and 'destructive' are coordinate adjectives modifying 'pests' and therefore require a comma, whereas 'insect' is a cumulative adjective (functioning as a noun adjunct) that should not be separated by a comma. Additionally, because the sentence starts with the subordinating conjunction 'Because', the introductory clause is dependent and must be separated from the main clause by a comma after 'pests'.

Step-by-Step Solution

1
Determine if the adjectives modifying 'pests' are coordinate or cumulative.
'Unpredictable' and 'destructive' are coordinate because they can be reversed and joined by 'and'. However, 'insect' is cumulative because it directly modifies 'pests' as a single unit ('insect pests').
Coordinate adjectives require a comma between them, while cumulative adjectives must not be separated by a comma.
2
Identify the clause boundary and determine the appropriate punctuation.
The sentence begins with the subordinating conjunction 'Because', making 'Because the regional agricultural board wanted to protect local crops from the unpredictable, destructive insect pests' a dependent clause.
An introductory dependent clause must be followed by a comma when it precedes an independent clause.
3
Evaluate the choices to find the one that applies both rules correctly.
The choice containing 'unpredictable, destructive insect pests, they recommended' is the only option that correctly includes the coordinate comma, excludes the cumulative comma, and uses a comma to separate the clauses.
This correctly resolves both the adjective punctuation and the clause boundary punctuation.

Key Concept

Punctuation of coordinate vs. cumulative adjectives and introductory dependent clauses
Estimated Time:1m 0s
Question 224Question →

Dorothy Hodgkin, a pioneer in X-ray crystallography, determined the structures of important biochemical substances. Her most famous breakthrough—the structure of penicillin, was resolved in 1945 after years of meticulous analysis.

Which of the following options is the best alternative to the underlined portion of the sentence?

Show answer & explanation

Answer: breakthrough—the structure of penicillin—was

Answer

breakthrough—the structure of penicillin—was
The correct answer properly utilizes matching em dashes to enclose the non-essential appositive phrase 'the structure of penicillin'. In standardized English grammar, non-essential elements must be set off with identical punctuation marks on both sides. Since an em dash is used to open the phrase, a second em dash must close it before the sentence's main verb.

Step-by-Step Solution

1
Identify the non-essential phrase in the sentence that provides additional, parenthetical information.
The phrase 'the structure of penicillin' is a non-essential appositive that clarifies what the 'most famous breakthrough' refers to.
Identifying the non-essential phrase helps determine that it must be set off from the rest of the sentence using consistent punctuation marks at both its start and end.
2
Evaluate the punctuation surrounding the non-essential phrase to ensure consistency.
An em dash is used immediately before the phrase. To maintain punctuation consistency, a matching em dash must be used immediately after the phrase before the main verb.
ACT grammar rules state that parenthetical elements must be enclosed by matching punctuation marks: either two commas, two parentheses, or two em dashes. Mixing an em dash with a comma is incorrect.

Key Concept

Using matching pairs of dashes to set off non-essential parenthetical information.
Estimated Time:45s
Question 225Question →

Although the dance troupe performed several complex routines, the dancers' choreographer worried about its reception among the traditional judges.

Which of the following choices represents the correct punctuation for the underlined portion of the sentence?

Show answer & explanation

Answer: NO CHANGE

Answer

NO CHANGE
The correct option correctly uses the plural possessive form 'dancers'' to describe the choreographer of the group of dancers within the troupe. It also correctly uses the possessive pronoun 'its' to refer to the reception of the troupe. Because the original phrasing is grammatically correct and appropriate in context, no changes are needed.

Step-by-Step Solution

1
Determine if the noun modifying 'choreographer' should be singular or plural, and possessive or not.
The sentence mentions a 'dance troupe,' which is a collective noun indicating a group of multiple dancers. The choreographer belongs to the dancers, so a plural possessive form is required.
This establishes that the correct noun form is the plural possessive 'dancers''.
2
Evaluate whether the pronoun referring to the 'reception' of the troupe should be a contraction or a possessive pronoun.
The sentence refers to the reception of the troupe (possessive), so the possessive pronoun 'its' is correct.
This distinguishes between the possessive pronoun 'its' and the contraction 'it's' (meaning 'it is' or 'it has').
3
Compare the original underlined portion against the identified correct forms.
The original text ('dancers' choreographer worried about its') uses both the plural possessive 'dancers'' and the possessive pronoun 'its' correctly, which matches the required grammatical rules.
This confirms that no change is necessary.

Key Concept

Apostrophes for Possessives and Contractions
Estimated Time:1m 0s
Question 226Question →

During their study of the nocturnal hunting habits of barn owls, researchers identified the birds' primary anatomical advantage; their asymmetric ear placement.

Which of the following is the best replacement for the underlined portion of the sentence?

Show answer & explanation

Answer: advantage: their

Answer

The option that replaces the semicolon with a colon ('advantage: their')
The correct option correctly uses a colon because the clause preceding it is independent and can stand alone as a complete sentence, while the noun phrase following it directly clarifies the 'advantage' mentioned.

Step-by-Step Solution

1
Analyze the clause preceding the punctuation mark to determine if it is independent.
The clause 'During their study of the nocturnal hunting habits of barn owls, researchers identified the birds' primary anatomical advantage' contains a subject ('researchers') and a verb ('identified') and functions as a complete sentence.
Both colons and semicolons require an independent clause before them.
2
Analyze the phrase following the punctuation mark to determine if it is independent.
The phrase 'their asymmetric ear placement' is a noun phrase without a verb and cannot stand alone as a complete sentence.
Since the second part is not an independent clause, a semicolon cannot be used.
3
Select the correct punctuation mark that links an independent clause to an explanatory noun phrase.
A colon is the appropriate mark because it is preceded by a complete sentence and followed by a phrase that explains the 'advantage'. Ensure the colon does not follow a verb directly.
This confirms that the choice placing a colon directly after the noun 'advantage' is grammatically correct.

Key Concept

A colon must be preceded by an independent clause and can be used to introduce an explanation, list, or clarifying noun phrase.
Estimated Time:45s
Question 227Question →

Read the sentence below about a scientific expedition. Which single punctuation mark must be placed in the blank to correctly separate the items in this complex list?

Fill in the blanks below

The research vessel carried a diverse team of scientists: Dr. Sylvia Earle, a marine biologist specializing in deep-sea algae; Dr. Robert Ballard, an oceanographer famous for locating historic shipwrecks and Dr. Cindy Lee Van Dover, a pioneer in hydrothermal vent ecology.
Show answer & explanation

Answer

A semicolon must be placed in the blank to correctly separate the complex list items.
The sentence lists three scientists, each followed by an appositive phrase containing a comma. When list items contain internal commas, semicolons must be used to separate the items to prevent confusion. A semicolon correctly distinguishes where one scientist's description ends and the next scientist's name begins.

Step-by-Step Solution

1
Identify the structure of the list in the sentence.
The sentence contains a list of three distinct scientists along with their descriptive titles.
Understanding the elements of the list helps determine the appropriate level of punctuation needed to separate them.
2
Analyze the punctuation within each list item.
Each list item contains internal punctuation (commas separating the scientist's name from their description).
Internal commas within list items require a stronger punctuation mark than a standard comma to separate the items themselves, avoiding confusion.
3
Determine the correct punctuation mark to separate these complex list items.
A semicolon is needed to separate the items in a complex list.
Semicolons are the standard punctuation mark used to separate items in a list when one or more of those items already contain internal commas.

Key Concept

Semicolons in complex lists
Question 228Question →

Astronomers studying the remote galaxy cluster observed a massive distortion in the surrounding space. The gravitational lens, which acts like a giant magnifying glass in space, allowed them to view stars from the early universe. This discovery could help researchers map the distribution of dark matter across the cosmos.

Which of the following is the best punctuation for the underlined portion of the passage?

Show answer & explanation

Answer: NO CHANGE

Answer

The original phrasing, which uses a pair of commas to enclose the nonessential relative clause, is correct.
The original sentence is correct. The clause 'which acts like a giant magnifying glass in space' is nonessential and must be enclosed by a pair of commas. The commas correctly isolate this parenthetical information from the subject 'lens' and its verb 'allowed'.

Step-by-Step Solution

1
Identify whether the underlined clause is essential or nonessential to the meaning of the sentence.
The clause 'which acts like a giant magnifying glass in space' provides descriptive detail about the gravitational lens but is not required to identify it or make the main clause complete. Therefore, it is a nonessential relative clause.
Determining the essentiality of a clause dictates how it should be punctuated.
2
Apply the punctuation rules for nonessential elements.
Nonessential elements must be set off from the rest of the sentence by a pair of commas (one before the clause and one after).
Properly enclosing parenthetical elements prevents grammatical errors like separating the subject from the verb.
3
Evaluate the choices to find the one that correctly implements the comma pair without introducing other errors.
The original sentence correctly places a comma before 'which' and a comma after 'space'.
This maintains the integrity of both the parenthetical information and the main clause.

Key Concept

Commas with Nonessential and Parenthetical Elements
Estimated Time:45s
Question 229Question →

In 1967, astrophysicist Jocelyn Bell Burnell detected a series of highly regular radio pulses while analyzing data from a newly constructed telescope. These strange signals, which were initially nicknamed 'Little Green Men' turned out to be the first evidence of rotating neutron stars. Today, these stars, known as pulsars, help astronomers map the structure of our galaxy.

Which of the following options represents the correct punctuation for the underlined portion?

Show answer & explanation

Answer: signals, which were initially nicknamed 'Little Green Men,' turned

Answer

The correct option is the one that places a comma both before and after the nonessential relative clause, resulting in: 'signals, which were initially nicknamed 'Little Green Men,' turned'
The clause 'which were initially nicknamed 'Little Green Men'' is a nonessential relative clause because the sentence remains grammatically complete and retains its core meaning without it. Nonessential elements must be set off by a pair of commas. Placing a comma after 'signals' and another after 'Men' correctly encloses the parenthetical information.

Step-by-Step Solution

1
Identify the clause following the noun 'signals'.
The clause 'which were initially nicknamed 'Little Green Men'' is a nonessential relative clause because it provides extra background information and is not necessary to identify which signals are being discussed.
Nonessential elements must be set off from the rest of the sentence with punctuation on both sides.
2
Determine the correct punctuation to enclose the nonessential clause.
Commas are the appropriate punctuation to set off this nonessential clause. A comma must be placed both before the clause (after 'signals') and after the clause (after 'Men').
Omitting either comma or using incorrect punctuation like a semicolon creates grammatical errors.

Key Concept

Commas with Nonessential and Parenthetical Elements
Estimated Time:45s
Question 230Question →

Although the software developers spent weeks refining the neural network's architecture; the unpredictable, complex, computer program crashed when exposed to the new dataset.

Which choice best punctuates the underlined portion of the sentence?

Show answer & explanation

Answer: architecture, the unpredictable, complex computer program crashed

Answer

architecture, the unpredictable, complex computer program crashed
The correct answer correctly places a comma after the introductory adverbial clause ending with 'architecture'. It also correctly places a single comma between the coordinate adjectives 'unpredictable' and 'complex' while omitting any punctuation between the cumulative modifier 'computer' and the noun 'program', and between the subject 'program' and its verb 'crashed'.

Step-by-Step Solution

1
Analyze the clause structure of the sentence.
The sentence begins with the subordinating conjunction 'Although', introducing a dependent adverbial clause: 'Although the software developers spent weeks refining the neural network's architecture'. This dependent clause must be joined to the subsequent independent clause using a comma, not a semicolon.
Semicolons are only used to connect two independent clauses, whereas a dependent clause must be followed by a comma when it introduces a sentence.
2
Evaluate the adjectives preceding the noun 'program' to determine if they are coordinate or cumulative.
The adjectives are 'unpredictable', 'complex', and 'computer'. 'Unpredictable' and 'complex' are coordinate because they can be reordered ('complex, unpredictable') and joined by 'and' ('unpredictable and complex') while retaining the original meaning. 'Complex' and 'computer' are cumulative because 'computer program' functions as a compound unit, and we cannot say 'complex and computer program'. Therefore, a comma must separate 'unpredictable' and 'complex', but no comma should follow 'complex' or separate 'computer' from 'program'.
Coordinate adjectives require separating commas, whereas cumulative adjectives and noun adjuncts do not.
3
Check the transition between the subject and the verb.
The subject 'program' should directly connect to the verb 'crashed' without any intervening punctuation.
A single comma should never separate a subject from its main verb.

Key Concept

Identifying introductory dependent clauses, distinguishing coordinate from cumulative adjectives, and avoiding incorrect punctuation between subjects and verbs.
Estimated Time:1m 15s
Question 231Question →

Read the passage below. Which punctuation mark should be placed in the blank to ensure the sentence is grammatically correct and internally consistent?

Fill in the blanks below

Though he never completed a working prototype, Charles Babbage envisioned a device that would lay the foundation for modern computing. The development of this theoretical machine—the Analytical Engine, a general-purpose computer designed to utilize punched cards for programming anticipated the digital age by nearly a century. Babbage’s collaborator, Ada Lovelace, even wrote the first algorithm intended for the engine, cementing their place in technological history.
Show answer & explanation

Answer

A dash (or em dash) is required to close the nonessential parenthetical phrase that begins with a dash.
A dash is required to close the parenthetical element. Because the parenthetical phrase starts with a dash after 'machine,' it must be closed with a matching dash after 'programming' to maintain consistent punctuation structure.

Step-by-Step Solution

1
Identify the nonessential parenthetical phrase within the sentence.
The phrase is 'the Analytical Engine, a general-purpose computer designed to utilize punched cards for programming'.
Determining where the parenthetical information begins and ends is necessary to apply the correct punctuation rules.
2
Examine the punctuation mark used to open the parenthetical phrase.
An em dash ('—') is placed immediately after 'theoretical machine' to introduce the parenthetical phrase.
Punctuation marks that set off nonessential information must be symmetrical and consistent.
3
Determine the correct punctuation mark for the blank to close the phrase.
Since the phrase began with a dash, it must close with a matching dash after 'programming'.
Mismatching punctuation marks (such as using a comma to close a phrase opened with a dash) is grammatically incorrect on the ACT.

Key Concept

Dash consistency in parenthetical elements
Question 232Question →

In 1938, a South African museum curator named Marjorie Courtenay-Latimer discovered an unusual blue fish among a local trawler's catch. The specimen, which had lobe-like fins and a three-lobed tail, was later identified as a coelacanth. Scientists were astonished because this lineage of fish was believed to have gone extinct over sixty million years ago.

Which choice correctly punctuates the underlined portion of the passage?

Show answer & explanation

Answer: NO CHANGE

Answer

The correct answer is the original phrasing, which correctly uses a pair of commas to enclose the nonessential relative clause.
The relative clause 'which had lobe-like fins and a three-lobed tail' is a nonessential (nonrestrictive) clause because it provides extra description about the specimen but is not required to identify it. Nonessential clauses must be set off from the rest of the sentence by a pair of commas. The original phrasing correctly places a comma before 'which' and a comma after 'tail'.

Step-by-Step Solution

1
Identify whether the underlined relative clause is essential (restrictive) or nonessential (nonrestrictive) to the meaning of the sentence.
The clause 'which had lobe-like fins and a three-lobed tail' provides descriptive detail about the specimen but is not needed to identify which specimen is being referred to. Therefore, the clause is nonessential.
Distinguishing between essential and nonessential information determines whether punctuation (like commas) is required to set off the clause.
2
Determine the correct punctuation rules for setting off a nonessential relative clause.
Nonessential clauses must be set off from the rest of the sentence by a pair of commas: one at the start of the clause and one at the end.
Using a pair of commas correctly signals to the reader that the enclosed information is parenthetical and can be omitted without changing the core meaning of the sentence.
3
Evaluate the options to find the one that correctly applies a pair of commas without creating other errors.
The original sentence correctly places a comma before 'which' and a comma after 'tail', meaning no change is needed.
This verifies that the original punctuation is correct and that the other options introduce punctuation errors like dangling commas, incorrect pronouns, or sentence fragments.

Key Concept

Commas with Nonessential and Parenthetical Elements
Estimated Time:1m 0s
Question 233Question →

Before the final spacecraft launch, the mission controllers double-checked the telemetry data. The controllers' primary worry was it's potential to be corrupted during transmission, which would jeopardize the entire landing sequence.

Which of the following options completes the underlined portion of the sentence in a grammatically correct way?

Show answer & explanation

Answer: controllers' primary worry was its

Answer

controllers' primary worry was its
The correct option properly uses 'controllers'' to show that the worry belongs to the plural group of controllers mentioned in the previous sentence. It also correctly uses 'its' as the possessive pronoun referring to the telemetry data.

Step-by-Step Solution

1
Determine if the noun 'controllers' should be singular or plural, and possessive.
The first sentence mentions 'mission controllers' (plural). Because the worry belongs to these controllers, a plural possessive form is needed, which is written as 'controllers''.
To show possession for a plural noun ending in 's', the apostrophe must go after the 's'.
2
Determine whether to use 'its' or 'it's'.
The sentence refers to the potential of the telemetry data. Therefore, the possessive pronoun 'its' is required.
'It's' is a contraction for 'it is' or 'it has', whereas 'its' is the possessive pronoun form.
3
Combine the correct plural possessive noun and the correct possessive pronoun.
The correct phrase is 'controllers' primary worry was its'.
This combination satisfies both the plural noun possession requirement and the possessive pronoun requirement.

Key Concept

Using plural possessive nouns and distinguishing between possessive pronouns and contractions
Question 234Question →

Read the passage below about thermophilic bacteria. Which punctuation mark should be placed in the blank to grammatically connect the two independent clauses?

Fill in the blanks below

Deep within the geothermal pools of Yellowstone National Park, microscopic organisms called thermophiles thrive in boiling water. These extreme microbes possess specialized proteins that do not denature at high temperatures researchers study these enzymes to develop more efficient PCR tests for medical diagnostics. Consequently, these tiny organisms have revolutionized the field of biotechnology.
Show answer & explanation

Answer

A semicolon (;) is the correct punctuation mark to connect the two independent clauses.
A semicolon is the correct punctuation mark because it is used to link two independent clauses that are closely related in thought, especially when there is no coordinating conjunction and the second clause starts with a lowercase letter.

Step-by-Step Solution

1
Analyze the clause preceding the blank.
The clause 'These extreme microbes possess specialized proteins that do not denature at high temperatures' is an independent clause because it contains a subject and a verb and can stand alone as a complete sentence.
To determine the appropriate punctuation, we must first establish the grammatical structure of the surrounding text.
2
Analyze the clause succeeding the blank.
The clause 'researchers study these enzymes to develop more efficient PCR tests for medical diagnostics' is also an independent clause.
Identifying the nature of both clauses helps us choose the correct punctuation mark to link them.
3
Select the correct punctuation mark to join two independent clauses without a coordinating conjunction.
A semicolon is required. Since the second clause begins with a lowercase letter, a period cannot be used. A comma alone would create a grammatically incorrect comma splice.
A semicolon is standard punctuation for connecting closely related independent clauses without a coordinating conjunction.

Key Concept

Using a semicolon to link two independent clauses that are closely related in thought.
Estimated Time:1m 0s
Question 235Question →

To maximize crop yields in urban areas, vertical farms rely on sophisticated automated systems: LED lighting, nutrient-rich mist, and climate sensors.

Which of the following choices best punctuates the underlined portion of the sentence?

Show answer & explanation

Answer: systems: LED lighting,

Answer

The correct option is the one that leaves the sentence unchanged, using a colon after 'systems' and before 'LED lighting' to introduce the list.
The correct answer properly uses a colon after the independent clause 'To maximize crop yields in urban areas, vertical farms rely on sophisticated automated systems' to introduce the list of items 'LED lighting, nutrient-rich mist, and climate sensors.' Under ACT English guidelines, a colon is the standard punctuation mark to introduce a list of items when it follows a complete sentence.

Step-by-Step Solution

1
Analyze the clause preceding the underlined portion.
The clause 'To maximize crop yields in urban areas, vertical farms rely on sophisticated automated systems' can stand alone as a complete sentence, making it an independent clause.
A colon can only be used if it is preceded by a complete, independent clause.
2
Examine the phrase that follows the underlined portion.
The phrase 'LED lighting, nutrient-rich mist, and climate sensors' is a list of three noun phrases that elaborates on the 'automated systems.'
A colon is the appropriate punctuation mark to introduce a list or explanation following an independent clause.
3
Evaluate the grammar of the remaining choices to eliminate incorrect alternatives.
The choice using 'systems, that include:' incorrectly places a colon after a verb. The choice using a semicolon incorrectly separates an independent clause from a noun phrase fragment. The choice using 'systems, they include' creates a comma splice by joining two independent clauses with only a comma.
Correct punctuation must avoid introducing fragments after semicolons, placing colons after verbs, or creating comma splices.

Key Concept

Use of colons to introduce lists after an independent clause
Question 236Question →

Early mariners relied on the astrolabe, a handheld instrument that calculated latitude by measuring the sun's angle. Navigators who sailed across the Atlantic, which could be unpredictable used the device to chart their courses. By the sixteenth century, this tool had transformed maritime exploration.

Which choice is the correct punctuation for the underlined portion of the passage?

Show answer & explanation

Answer: who sailed across the Atlantic, which could be unpredictable,

Answer

who sailed across the Atlantic, which could be unpredictable,
The correct answer properly leaves the restrictive clause 'who sailed across the Atlantic' unpunctuated while using a pair of commas to set off the nonessential relative clause 'which could be unpredictable'. This ensures that the subject 'Navigators' is directly connected to its modifier, and the extra parenthetical information is correctly separated from the main sentence structure.

Step-by-Step Solution

1
Identify the clauses in the underlined portion and determine whether they are restrictive (essential) or nonessential (parenthetical).
The clause 'who sailed across the Atlantic' is restrictive because it defines which specific navigators used the device. The clause 'which could be unpredictable' is nonessential because it adds extra information about the Atlantic but is not necessary to identify the ocean.
Restrictive clauses do not receive commas, while nonessential clauses must be enclosed in a pair of commas.
2
Evaluate the punctuation needed for both clauses.
No commas should surround 'who sailed across the Atlantic'. A comma must precede 'which' and another comma must follow 'unpredictable' to close the nonessential clause.
This maintains the grammatical separation of parenthetical information without interrupting the relationship between the subject 'Navigators' and its modifier.

Key Concept

Distinguishing between restrictive and nonessential clauses to apply correct comma punctuation.
Question 237Question →

In 1964, radio astronomers Arno Penzias and Robert Wilson detected a persistent background hiss that they could not explain, they initially suspected that the noise was caused by nesting pigeons. However, even after cleaning the antenna, the signal remained. This mysterious hum was actually the cosmic microwave background radiation, which is the remnant heat of the Big Bang.

Which of the following is the best choice for the underlined portion of the passage?

Show answer & explanation

Answer: explain. They

Answer

The correct option separates the two independent clauses into two distinct sentences using a period: 'explain. They'
The correct option correctly uses a period to separate two independent clauses into two distinct sentences. Both 'In 1964, radio astronomers Arno Penzias and Robert Wilson detected a persistent background hiss that they could not explain' and 'They initially suspected that the noise was caused by nesting pigeons' are complete thoughts with their own subjects and verbs.

Step-by-Step Solution

1
Identify the clauses surrounding the underlined portion.
The clause before the underline is 'In 1964, radio astronomers Arno Penzias and Robert Wilson detected a persistent background hiss that they could not explain' and the clause after is 'they initially suspected that the noise was caused by nesting pigeons'.
To determine correct punctuation, you must first verify whether the clauses are independent or dependent.
2
Determine if each clause can stand alone as a complete sentence.
Both clauses contain a subject and a verb and express a complete thought, meaning they are both independent clauses.
Understanding clause type guides which punctuation marks are grammatically acceptable.
3
Select the punctuation that correctly separates these two independent clauses.
A period correctly separates the two clauses into two complete sentences.
Joining two independent clauses with only a comma creates a comma splice, while options containing subordinating conjunctions ('although' or 'because') turn the second clause into an ungrammatical sentence fragment.

Key Concept

End-of-Sentence Punctuation
Estimated Time:1m 0s
Question 238Question →

To survive in nutrient-poor bogs, the Venus flytrap relies on a highly specialized trapping mechanism consisting of; sensitive trigger hairs that detect movement, rapid leaf closure, and digestive enzymes.

Which of the following options correctly punctuates the underlined portion of the sentence?

Show answer & explanation

Answer: mechanism: sensitive trigger hairs

Answer

The correct answer is the option that replaces the underlined text with a colon after the word 'mechanism' followed by the list of items.
The correct option replaces the underlined portion with a colon after the independent clause ending with 'mechanism'. This is correct because the preceding clause is independent and the colon properly introduces the subsequent list of three features.

Step-by-Step Solution

1
Identify the clause preceding the punctuation mark.
The clause 'To survive in nutrient-poor bogs, the Venus flytrap relies on a highly specialized trapping mechanism' is an independent clause because it contains a subject and a verb and can stand alone as a complete sentence.
A colon can only be placed after a clause that is complete and independent.
2
Analyze the grammatical structure of the elements following the punctuation.
The elements 'sensitive trigger hairs that detect movement, rapid leaf closure, and digestive enzymes' form a list of noun phrases rather than a complete sentence.
This determines that a colon is appropriate to introduce the list, whereas a semicolon is incorrect because the second part is not an independent clause.
3
Evaluate the placement of the colon in relation to prepositions or verbs.
Placing a colon directly after 'consisting of' is grammatically incorrect because it disrupts the flow between the prepositional participle and its object list.
A colon should never separate a verb or preposition from its direct objects or complements.

Key Concept

A colon must be preceded by a complete independent clause and can be used to introduce a list, explanation, or amplification.
Estimated Time:45s
Question 239Question →

Read the passage below about the construction of the Florence Cathedral. What punctuation mark should be placed in the blank to grammatically complete the second sentence?

Fill in the blanks below

Filippo Brunelleschi faced a daunting challenge when he was commissioned to build the dome of the Florence Cathedral. Many citizens wondered how the architect could construct such a massive structure without wooden scaffolding He ultimately succeeded by using an innovative herringbone brick-laying pattern. This technique distributed the weight outward rather than downward.
Show answer & explanation

Answer

A period (.) is the correct punctuation mark to end the sentence.
The sentence containing the blank is an indirect question, which functions grammatically as a declarative statement. Consequently, it must end with a period. A question mark would be incorrect because the sentence does not ask a direct question.

Step-by-Step Solution

1
Analyze the sentence containing the blank to determine its grammatical structure.
The sentence begins with 'Many citizens wondered how...', which introduces an indirect question.
This step determines whether the sentence is a direct question requiring a question mark or a statement requiring a period.
2
Determine the correct punctuation mark for the sentence boundary.
Since indirect questions function as declarative statements, they must end with a period rather than a question mark.
An indirect question does not take a question mark because it reports a question rather than asking it directly.

Key Concept

Indirect questions are grammatically declarative sentences and must end with a period rather than a question mark.
Question 240Question →

In the damp forests of southern Brazil, a rare species of bioluminescent mushroom glows with a vibrant green light. To attract nocturnal insects for spore dispersal, the fungus relies on a distinct ecological mechanism: a constant green glow fueled by chemical reactions in its cells.

Which of the following choices best punctuates the underlined portion of the sentence?

Show answer & explanation

Answer: mechanism: a constant green glow

Answer

mechanism: a constant green glow
The correct answer correctly uses a colon to separate an independent clause from a clarifying noun phrase that explains the 'mechanism' mentioned. Because the preceding clause is independent, and the following phrase serves as a definition or explanation, the colon is the standard and correct punctuation choice.

Step-by-Step Solution

1
Analyze the clause preceding the punctuation mark.
The clause 'To attract nocturnal insects for spore dispersal, the fungus relies on a distinct ecological mechanism' is independent and can stand alone as a complete sentence.
Determining if the preceding clause is independent is the first step in deciding whether a colon or semicolon is appropriate.
2
Analyze the phrase following the punctuation mark.
The phrase 'a constant green glow fueled by chemical reactions in its cells' is a noun phrase, not an independent clause.
Since the following phrase is dependent, a semicolon cannot be used, but a colon is permissible if it introduces a clarification or explanation.
3
Evaluate the choices to find the one that correctly connects the clauses without interrupting the grammatical flow.
The choice using a colon directly after 'mechanism' is correct. The other choices either use a semicolon incorrectly or insert a colon after a verb or preposition.
A colon is correctly used to join an independent clause to a dependent clarifying phrase, while avoiding misplaced colons after verbs or prepositions.

Key Concept

Colons must be preceded by an independent clause and should not be placed immediately after a verb or preposition.
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Conventions of Punctuation Practice Questions — ACT — Page 12 | Examkin