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Difficulty: MediumCommas with Lists, Clauses, and Coordinate Adjectives

During nocturnal field observations in tropical rainforests, entomologists recorded firefly species that produced rhythmic bright flashes, and they transmitted these signals across the dense canopy. Which choice best completes the sentence according to the conventions of standard written English?

  1. A
    NO CHANGE
  2. , bright flashes, and they transmittedAnswer
  3. C
    , bright flashes, they transmitted
  4. D
    , bright flashes; and they transmitted

Answer

The choice containing ', bright flashes, and they transmitted' correctly punctuates the sentence.
The correct response inserts a comma between the coordinate adjectives 'rhythmic' and 'bright' because both adjectives independently modify 'flashes'. Furthermore, it retains the comma prior to the coordinating conjunction 'and' to properly separate two complete independent clauses.

Step-by-Step Solution

1
Determine if 'rhythmic' and 'bright' are coordinate adjectives.
Because both 'rhythmic' and 'bright' modify 'flashes' independently (e.g., one can say 'rhythmic and bright flashes'), a comma is required between them.
Coordinate adjectives that modify the same noun must be separated by a comma.
2
Analyze the clause structure following the noun phrase.
The clause 'they transmitted these signals across the dense canopy' is independent because it contains its own subject ('they') and verb ('transmitted').
When two independent clauses are joined by a coordinating conjunction like 'and', a comma must precede the conjunction.
3
Select the option meeting both punctuation requirements.
The correct selection provides a comma after 'rhythmic' (yielding 'rhythmic, bright flashes') and keeps the comma before 'and' to connect the main clauses.
This satisfies standard English punctuation rules for both coordinate adjectives and compound independent clauses.

Key Concept

Commas with Coordinate Adjectives and Independent Clauses
Estimated Time:1m 0s
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Topics

Commas with Lists, Clauses, and Coordinate Adjectives

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