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Question

Difficulty: MediumDashes

The passage below contains a blank indicating a missing punctuation mark. Fill in the blank with the punctuation mark that correctly completes the sentence, maintaining consistency with the punctuation already used to set off the nonessential clause.

Answer:In 1967, astrophysicist Jocelyn Bell Burnell detected a series of repeating radio signals—initially dubbed 'Little Green Men' as a joke【—】that turned out to be the first discovered pulsar.

Answer

An em dash (—) or double hyphen (--) must be used to close the nonessential parenthetical phrase.
The sentence uses an em dash (—) to open the nonessential parenthetical phrase 'initially dubbed "Little Green Men" as a joke'. Under standard punctuation rules tested on the ACT, nonessential phrases set off by dashes must be closed with a matching dash. Therefore, an em dash (—) or its keyboard representation (--) is required to correctly complete the sentence.

Step-by-Step Solution

1
Identify the parenthetical (nonessential) clause in the sentence.
The phrase 'initially dubbed "Little Green Men" as a joke' provides extra, nonessential information about the radio signals.
Nonessential information must be set off from the rest of the sentence by matching punctuation marks on both sides.
2
Examine the punctuation mark that opens the parenthetical clause.
An em dash (—) precedes 'initially'.
This establishes that dashes are being used as the punctuation style for this parenthetical element.
3
Determine the matching punctuation mark needed to close the parenthetical clause.
Another em dash (—) or double hyphen (--) is required before 'that'.
To maintain punctuation consistency, a dash must be paired with another dash; pairing a dash with a comma, semicolon, or parenthesis is incorrect.

Key Concept

Punctuation consistency with parenthetical elements requires using matching marks (dash with dash, comma with comma, parenthesis with parenthesis) to set off nonessential information.
Estimated Time:45s
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Topics

Dashes

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