Examkin

Question

Difficulty: MediumPunctuation of Nonessential Elements

Read the passage below. What punctuation mark should be placed in the blank to correctly set off the nonessential element?

Answer:In 1970, marine biologist Sylvia Earle led the first all-female team of aquanauts in the Tektite II project, an underwater laboratory in the Virgin Islands. During the mission, Earle—who spent weeks studying marine life at a depth of fifty feet 【—】 observed the devastating effects of pollution on coral reefs.

Answer

An em dash (—)
The sentence includes the nonessential relative clause 'who spent weeks studying marine life at a depth of fifty feet.' Because this clause is introduced with an em dash after the subject 'Earle,' it must also close with a matching em dash before the main verb 'observed' to maintain punctuation symmetry.

Step-by-Step Solution

1
Identify the nonessential element in the target sentence.
The clause 'who spent weeks studying marine life at a depth of fifty feet' is a nonessential relative clause describing the subject 'Earle'.
Nonessential clauses provide extra details that are not grammatically necessary for the main clause to function.
2
Determine the punctuation mark used to introduce the nonessential element.
An em dash (—) is placed right before the relative pronoun 'who'.
Nonessential elements must be set off with a matching pair of punctuation marks to maintain grammatical symmetry.
3
Select the correct punctuation mark to close the nonessential element.
An em dash (—) must be placed in the blank before the main verb 'observed' to match the opening em dash.
Using any other punctuation mark, such as a comma, would violate punctuation symmetry.

Key Concept

Punctuation of Nonessential Elements
Rate this question

Topics

Punctuation of Nonessential Elements

More questions from this topic