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Difficulty: Very hardColons

Although some evolutionary biologists initially hypothesized that the unique structure of the narwhal’s tusk served primarily as a weapon for defense, recent sensory research suggests a far more complex purpose: it acts as a hydrodynamic sensor containing millions of nerve endings.

Which of the following options best replaces the underlined portion of the sentence?

  1. purpose: it acts as a hydrodynamic sensor containingAnswer
  2. B
    purpose, which is: a hydrodynamic sensor containing
  3. C
    purpose; acting as a hydrodynamic sensor containing
  4. D
    purpose, it acts as a hydrodynamic sensor containing

Answer

The option that uses a colon to connect the first independent clause to the second explanatory independent clause is correct.
The colon is correctly used to connect an independent clause to a second independent clause that explains, illustrates, or expands on the first. The clause before the colon is independent, and the explanation following it is grammatically complete and directly elaborates on the 'purpose' mentioned.

Step-by-Step Solution

1
Analyze the grammatical structure of the clause preceding the punctuation mark.
The clause 'Although some evolutionary biologists initially hypothesized that the unique structure of the narwhal’s tusk served primarily as a weapon for defense, recent sensory research suggests a far more complex purpose' is an independent clause.
Both colons and semicolons require an independent clause before them.
2
Analyze the grammatical structure of the phrase or clause following the punctuation mark.
The phrase 'it acts as a hydrodynamic sensor containing millions of nerve endings' is a complete independent clause that explains the 'purpose' mentioned previously.
This determines whether a colon, semicolon, or other punctuation is required.
3
Evaluate the choices to select the punctuation that correctly connects these clauses without creating errors.
A colon is appropriate to introduce the explanation. The semicolon option creates a fragment, the comma option creates a comma splice, and placing a colon after 'is' is incorrect.
Only the colon correctly connects the explanation to the preceding independent clause.

Key Concept

Colon punctuation rules
Estimated Time:1m 0s
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Topics

Colons

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