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Difficulty: HardCommas with Lists, Clauses, and Coordinate Adjectives

To determine the age of the ancient timber, the dendrochronologists extracted several thin cylindrical, core samples, and they examined the growth rings under a high-powered microscope.

Which choice best punctuates the underlined portion of the sentence?

  1. A
    NO CHANGE
  2. thin, cylindrical core samples, and they examinedAnswer
  3. C
    thin, cylindrical core samples, they examined
  4. D
    thin, cylindrical core samples; examining

Answer

The correct choice is the one that punctuates the coordinate adjectives with a comma ('thin, cylindrical'), keeps the cumulative adjective and noun modifier unpunctuated ('core samples'), and uses a comma before the coordinating conjunction 'and' to connect the two independent clauses.
The correct choice properly applies the rules of punctuation for coordinate adjectives and independent clauses. The adjectives 'thin' and 'cylindrical' are coordinate because they can be reversed and joined by 'and' while maintaining a natural sound; therefore, a comma must separate them. The word 'core' acts as a noun adjunct modifying 'samples,' making 'cylindrical' and 'core' cumulative adjectives, which should not be separated by a comma. Finally, the sentence contains two independent clauses joined by the coordinating conjunction 'and,' which requires a comma beforehand to avoid a run-on sentence.

Step-by-Step Solution

1
Analyze the relationship between the adjectives modifying the noun phrase 'core samples'.
The adjectives 'thin' and 'cylindrical' are coordinate adjectives because they can be reversed ('cylindrical, thin') and connected by 'and' ('thin and cylindrical') naturally. Therefore, they require a comma between them. However, 'core' acts as a noun adjunct modifying 'samples,' making 'cylindrical' and 'core' cumulative adjectives, which should not have a comma between them.
To determine the correct punctuation between modifiers and the noun.
2
Identify the clause structure of the entire sentence to determine the correct conjunction and punctuation.
The sentence consists of two independent clauses: 'the dendrochronologists extracted several thin, cylindrical core samples' and 'they examined the growth rings...'. These two complete thoughts are joined by the coordinating conjunction 'and,' which requires a comma before it.
To ensure correct connection of independent clauses and avoid run-on sentences or comma splices.
3
Evaluate the remaining options against the rules identified in Steps 1 and 2.
The correct choice must read: 'thin, cylindrical core samples, and they examined'. The other options fail by omitting the required comma between coordinate adjectives, separating the adjective from its noun, creating a comma splice, or creating a sentence fragment with an incorrect semicolon.
To select the grammatically correct option that fits all rules.

Key Concept

Commas with Lists, Clauses, and Coordinate Adjectives
Estimated Time:1m 0s
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Topics

Commas with Lists, Clauses, and Coordinate Adjectives

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