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Difficulty: Very hardColons

In 1967, astrophysicist Jocelyn Bell Burnell observed a series of regular radio pulses that she initially nicknamed 'Little Green Men'; however, further analysis revealed the source to be a rapidly spinning neutron star, it is a pulsar, which emits electromagnetic radiation along its magnetic poles.

Which of the following is the correct punctuation and phrasing for the underlined portion of the sentence?

  1. A
    NO CHANGE
  2. star: a pulsar, which emitsAnswer
  3. C
    star, which was: a pulsar that emits
  4. D
    star, a pulsar. Which emits

Answer

The correct option is the phrasing that reads 'star: a pulsar, which emits', as it uses a colon after a complete independent clause to introduce a clarifying definition.
The phrasing that uses a colon to introduce the appositive phrase defining the neutron star is correct. The clause before the colon is fully independent, and the information after it serves to clarify the specific type of star, which is the proper function of a colon.

Step-by-Step Solution

1
Determine if the clause before the underlined portion is independent.
The clause 'In 1967, astrophysicist Jocelyn Bell Burnell observed a series of regular radio pulses that she initially nicknamed 'Little Green Men'; however, further analysis revealed the source to be a rapidly spinning neutron star' is a complete thought that can stand alone as a sentence.
According to punctuation rules, a colon must be preceded by a complete independent clause.
2
Evaluate the grammatical relationship of the information following the punctuation.
The phrase 'a pulsar, which emits electromagnetic radiation along its magnetic poles' acts as an appositive that clarifies and defines the 'neutron star'.
A colon is used to introduce an explanation, definition, or list that elaborates on the preceding independent clause.
3
Analyze and eliminate incorrect distractors based on punctuation errors.
The original phrasing creates a comma splice; placing a colon after 'was' creates an incomplete clause before the colon; separating the relative clause with a period creates a sentence fragment.
Eliminating these errors leaves only the correct use of the colon to connect the independent clause to its clarifying appositive.

Key Concept

A colon must be preceded by an independent clause and is used to introduce an explanation, definition, illustration, or list that clarifies the preceding clause.
Estimated Time:45s
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Colons

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