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Question

Difficulty: Very hardColons

Biologists studying the isolated Tepui tablelands of South America have observed a rare ecological phenomenon: evolutionary stasis, which is the preservation of ancestral traits over millions of years.

Which of the following options best replaces the underlined portion of the sentence?

  1. phenomenon: evolutionary stasis, which isAnswer
  2. B
    phenomenon, this is evolutionary stasis, which is
  3. C
    phenomenon that is: evolutionary stasis, which is
  4. D
    phenomenon; which is evolutionary stasis,

Answer

phenomenon: evolutionary stasis, which is
The correct answer is the option that keeps the colon after 'phenomenon' because the preceding clause is independent, and the colon appropriately introduces the explanation of the phenomenon ('evolutionary stasis'). The comma after 'stasis' correctly introduces the nonessential relative clause.

Step-by-Step Solution

1
Determine if the clause before the punctuation mark is independent.
The clause 'Biologists studying the isolated Tepui tablelands of South America have observed a rare ecological phenomenon' is independent because it contains a subject and a verb and can stand alone as a complete sentence.
Colons must be preceded by a complete independent clause.
2
Evaluate the structure of the phrase following the punctuation mark.
The phrase 'evolutionary stasis, which is the preservation...' is a noun phrase followed by a nonessential relative clause, meaning it is a dependent phrase.
This helps rule out punctuation marks like semicolons, which require independent clauses on both sides.
3
Apply grammar rules to test the punctuation choices.
A colon is appropriate here because it follows an independent clause and introduces an explanation. Using a semicolon creates a fragment, using a comma with 'this is' creates a comma splice, and putting the colon after 'that is' leaves the preceding clause incomplete.
To identify the only grammatically correct option.

Key Concept

A colon must be preceded by an independent clause and can be used to introduce an explanation, list, or clarification.

Alternative Method

Try reading the sentence up to the colon. If it cannot stand alone as a complete sentence, a colon cannot be used. If it can, verify that the following part explains or defines what came before.
Estimated Time:45s
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Topics

Colons

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