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Difficulty: MediumCommas with Nonessential and Parenthetical Elements

During the 1900 yellow fever epidemic in Havana, Dr. Walter Reed led a U.S. Army commission to identify the transmission method of the deadly disease. Reed's subsequent [1] experiments, which confirmed Carlos Finlay's mosquito hypothesis, saved thousands of lives. This crucial discovery paved the way for the eradication of yellow fever in the region.

Which of the following is the most appropriate punctuation for the underlined portion marked [1]?

  1. NO CHANGEAnswer
  2. B
    experiments, that confirmed Carlos Finlay's mosquito hypothesis,
  3. C
    experiments, which confirmed Carlos Finlay's mosquito hypothesis
  4. D
    experiments; which confirmed Carlos Finlay's mosquito hypothesis,

Answer

The correct answer is the option that makes no change to the passage, as it correctly uses a pair of commas to enclose the nonessential relative clause.
The clause 'which confirmed Carlos Finlay's mosquito hypothesis' is nonessential because the experiments are already specified as Reed's subsequent ones. Enclosing this nonessential relative clause with a pair of commas correctly separates it from the main clause.

Step-by-Step Solution

1
Determine if the underlined clause is essential or nonessential to the sentence.
The clause 'which confirmed Carlos Finlay's mosquito hypothesis' provides extra information about 'Reed's subsequent experiments' but is not needed to identify which experiments are being discussed. Therefore, the clause is nonessential.
Nonessential elements must be set off from the rest of the sentence by punctuation on both sides.
2
Select the correct punctuation to set off the nonessential relative clause.
A pair of commas must enclose the clause, meaning a comma is needed after 'experiments' and another comma is needed after 'hypothesis'.
Enclosing parenthetical information with a pair of commas is the standard grammatical convention to prevent run-on structures or dangling commas.
3
Eliminate incorrect options based on grammatical errors.
Using 'that' with commas is incorrect because 'that' introduces restrictive clauses. Omitting the second comma leaves a single comma dangling. Using a semicolon creates a fragment because a dependent clause cannot follow a semicolon.
Applying standard rules of commas and semicolons helps identify the single grammatically correct choice.

Key Concept

Commas with Nonessential and Parenthetical Elements
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Topics

Commas with Nonessential and Parenthetical Elements

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