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Difficulty: MediumCommas with Nonessential and Parenthetical Elements

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?

  1. NO CHANGEAnswer
  2. B
    lens, which acts like a giant magnifying glass in space
  3. C
    lens; which acts like a giant magnifying glass in space,
  4. D
    lens, that acts like a giant magnifying glass in space,

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
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Topics

Commas with Nonessential and Parenthetical Elements

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