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Difficulty: MediumSubject-Verb Agreement

In astrobiology, researchers analyze distant worlds for environments capable of supporting organisms. The detection of potential biosignatures—specifically atmospheric methane and oxygen found in precise ratios on rocky exoplanets orbiting distant stars—______ that biological processes may be occurring elsewhere in the galaxy. However, astronomers must remain cautious, as abiotic geochemical reactions can also synthesize these atmospheric gases under specific conditions.

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

  1. A
    suggesting
  2. suggestsAnswer
  3. C
    suggest
  4. D
    have suggested

Answer

suggests
The correct answer is 'suggests' because it is a singular, present-tense verb that agrees with the singular subject 'The detection'. The long intervening modifier contains multiple plural nouns, but these do not alter the singular agreement required by the sentence's primary subject.

Step-by-Step Solution

1
Locate the subject of the target sentence.
The subject of the sentence is the singular noun phrase 'The detection'.
To ensure subject-verb agreement, the verb must match the grammatical number of this primary subject.
2
Analyze the intervening phrase to isolate the subject from modifying nouns.
The phrase 'of potential biosignatures—specifically atmospheric methane and oxygen found in precise ratios on rocky exoplanets orbiting distant stars—' acts as a modifier. Plural nouns within this modifier, such as 'biosignatures' and 'exoplanets', do not change the singular nature of the subject.
Nouns inside prepositional or parenthetical phrases do not affect subject-verb agreement.
3
Select the verb form that agrees with the singular subject and matches the active present-tense context of the passage.
The singular verb 'suggests' correctly matches the singular subject 'detection'.
Plural forms and non-finite verb forms create grammatical agreement errors or fragment errors.

Key Concept

Subject-Verb Agreement
Estimated Time:1m 0s
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Topics

Subject-Verb Agreement

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