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Difficulty: MediumCommas with Nonessential and Parenthetical Elements

During the expedition, the research team gathered various ice cores. The samples, which were collected from the Antarctic shelf contained ancient air bubbles that reveal details about the Earth's historic atmosphere. By analyzing these tiny pockets of gas, scientists can reconstruct past climates.

Which option most effectively corrects the punctuation of the underlined portion in the passage?

  1. A
    NO CHANGE
  2. samples, which were collected from the Antarctic shelf, containedAnswer
  3. C
    samples, that were collected from the Antarctic shelf, contained
  4. D
    samples; which were collected from the Antarctic shelf, contained

Answer

The correct option is the one that sets off the nonessential relative clause with a pair of commas: 'samples, which were collected from the Antarctic shelf, contained'.
The correct answer properly identifies that the relative clause describing the ice core samples is nonessential and therefore must be set off with a pair of commas. The punctuation correctly places a comma before the relative pronoun 'which' and a second comma after 'shelf' to close the parenthetical insertion before the main verb 'contained'.

Step-by-Step Solution

1
Identify whether the underlined clause is essential (restrictive) or nonessential (nonrestrictive) to the meaning of the sentence.
The clause 'which were collected from the Antarctic shelf' is nonessential because the sentence still identifies 'The samples' as the subject and makes sense without this additional descriptive detail.
Nonessential elements must be set off from the rest of the sentence with punctuation (usually commas), while essential elements should not have commas.
2
Select the option that correctly uses a pair of commas to enclose the nonessential relative clause.
The correct option uses a comma after 'samples' and a comma after 'shelf' before the verb 'contained'.
This maintains the grammatical flow and correctly punctuates the parenthetical information.

Key Concept

Commas with Nonessential and Parenthetical Elements
Estimated Time:1m 0s
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Topics

Commas with Nonessential and Parenthetical Elements

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