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Difficulty: MediumCommas with Nonessential and Parenthetical Elements

The following passage is an excerpt from an essay on the history of science.

In the mid-twentieth century, the scientific community remained skeptical of plate tectonics. Marie Tharp, a pioneering cartographer, created the ocean map that proved the theory of continental drift. Her meticulous work revealed the dramatic topography of the ocean floor, transforming geology forever.

Which choice is the correct punctuation for the underlined portion of the sentence?

  1. NO CHANGEAnswer
  2. B
    Tharp, a pioneering cartographer created the ocean map that proved the theory of continental drift
  3. C
    Tharp, a pioneering cartographer, created the ocean map, that proved the theory of continental drift,
  4. D
    Tharp; a pioneering cartographer, created the ocean map that proved the theory of continental drift

Answer

NO CHANGE
The correct choice properly uses a pair of commas to set off the nonessential appositive 'a pioneering cartographer' while leaving the restrictive relative clause 'that proved the theory of continental drift' unpunctuated.

Step-by-Step Solution

1
Identify nonessential elements in the sentence.
The phrase 'a pioneering cartographer' is an appositive describing Marie Tharp. Since removing it does not change the core meaning of the sentence, it is nonessential and must be enclosed by a pair of commas.
Nonessential appositives require punctuation on both sides to set them apart from the rest of the sentence.
2
Identify restrictive elements in the sentence.
The relative clause 'that proved the theory of continental drift' is restrictive because it defines exactly which ocean map is being referred to. It should not be set off by commas.
Restrictive clauses are essential to the meaning of the sentence and must not be separated from their referent.
3
Evaluate the option choices against these rules.
Only the original phrasing ('NO CHANGE') correctly uses a pair of commas for the appositive and leaves the restrictive clause unpunctuated.
This maintains correct grammatical structure and sentence clarity.

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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