Examkin

Question

Difficulty: MediumColons, Semicolons, and Dashes

Although the thick, sulfur-rich clouds of Venus completely obscure its surface from visible-light telescopes, scientists have successfully mapped the planet's complex topography. To bypass this atmospheric barrier, the Magellan spacecraft utilized synthetic aperture radar ______ a sophisticated technology that transmitted microwave pulses through the cloud layer and measured the reflected signals to construct highly detailed three-dimensional maps of the Venusian terrain.

Which choice completes the text so that it conforms to the conventions of Standard English?

  1. —aAnswer
  2. B
    ; a
  3. C
    , it was a
  4. D
    a

Answer

The choice containing a single dash followed by 'a' ('—a') is correct because it appropriately sets off the explanatory appositive phrase that describes 'synthetic aperture radar'.
The correct option uses a single dash to link the independent clause to the explanatory appositive noun phrase ('a sophisticated technology...'). A single dash is an acceptable punctuation mark to introduce explanatory details, lists, or summaries at the end of an independent clause.

Step-by-Step Solution

1
Analyze the structure of the clause preceding the blank.
The clause 'To bypass this atmospheric barrier, the Magellan spacecraft utilized synthetic aperture radar' is an independent clause because it contains a subject and a verb and can stand alone as a sentence.
Determining the grammatical status of the preceding clause helps identify which punctuation marks (such as colons, semicolons, or dashes) are permitted.
2
Analyze the structure of the phrase following the blank.
The phrase starting with 'a sophisticated technology...' is a noun phrase (an appositive) that explains 'synthetic aperture radar'; it is not an independent clause.
Knowing whether the following phrase is an independent or dependent clause rules out punctuation marks that require independent clauses on both sides, such as semicolons.
3
Evaluate the punctuation choices based on grammatical rules.
A single dash is correct for connecting an independent clause to an explanatory noun phrase. A semicolon is incorrect because the second part is not an independent clause. A comma splice is created by inserting a subject and verb ('it was') after a comma, and omitting punctuation entirely creates a run-on.
Matching the structural requirements of the sentence to the conventions of Standard English identifies the correct option.

Key Concept

Using a single dash to set off explanatory details at the end of an independent clause, and distinguishing it from semicolon and comma splice errors.
Rate this question

Topics

Colons, Semicolons, and Dashes

More questions from this topic