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Difficulty: MediumCommas with Nonessential and Parenthetical Elements

In 2009, chemist Mas Subramanian and his team at Oregon State University accidentally discovered YInMn Blue while researching materials for electronics. The vibrant pigment, which is the first new blue discovered in over two centuries, contains elements of yttrium, indium, and manganese. Because it reflects infrared light, it could also help keep buildings cool if used as paint.

Which choice most correctly punctuates the underlined portion of the passage?

  1. NO CHANGEAnswer
  2. B
    pigment, which is the first new blue discovered in over two centuries contains
  3. C
    pigment; which is the first new blue discovered in over two centuries, contains
  4. D
    pigment, that is the first new blue discovered in over two centuries, contains

Answer

The choice that reads 'NO CHANGE' is correct because it properly encloses the nonessential relative clause with a pair of commas.
The correct answer properly uses a pair of commas to enclose the nonessential relative clause 'which is the first new blue discovered in over two centuries'. Because 'The vibrant pigment' is already defined, this clause acts as parenthetical information that can be removed without changing the core meaning of the sentence. Therefore, it must be separated from the rest of the sentence by commas on both sides.

Step-by-Step Solution

1
Analyze the underlined portion to determine if the relative clause 'which is the first new blue discovered in over two centuries' is essential (restrictive) or nonessential (nonrestrictive).
The clause is nonessential because the subject 'The vibrant pigment' is already specific and its identity does not depend on the relative clause.
Nonessential elements must be set off from the rest of the sentence by punctuation, usually commas.
2
Check the punctuation around the nonessential clause in each option to find the grammatically correct arrangement.
The original phrasing correctly uses a comma before 'which' and a comma after 'centuries' to enclose the clause.
This configuration correctly sets off the parenthetical information, whereas other choices omit one comma, create a fragment with a semicolon, or use commas around a restrictive 'that' clause.

Key Concept

Commas with Nonessential and Parenthetical Elements
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Topics

Commas with Nonessential and Parenthetical Elements

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