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Question

Difficulty: EasySubject-Verb Agreement

In the absolute darkness of the ocean's midnight zone, the survival of extremophilic bacteria near hydrothermal vents ______ heavily on chemosynthesis rather than photosynthesis. Because sunlight cannot reach these extreme depths, these microscopic organisms must convert dissolved sulfur compounds into usable energy, forming the foundation of a unique deep-sea food web.

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

  1. reliesAnswer
  2. B
    rely
  3. C
    relying
  4. D
    have relied

Answer

The correct option is 'relies' because it is a singular verb that correctly agrees with the singular subject 'survival'.
The singular present-tense verb 'relies' correctly agrees with the singular subject 'survival'. Intervening prepositional phrases containing plural nouns like 'bacteria' and 'vents' do not affect the number of the subject.

Step-by-Step Solution

1
Identify the subject of the target verb.
The subject is the singular noun 'survival'. The plural nouns 'bacteria' and 'vents' are part of the intervening prepositional phrase ('of extremophilic bacteria near hydrothermal vents') and do not determine verb agreement.
Subject-verb agreement is determined by the head noun of the subject noun phrase, not by nouns within modifying prepositional phrases.
2
Determine the correct verb form that matches the subject in number.
The verb must be singular to match the singular subject 'survival'. The present tense verb form 'relies' is singular and grammatically fits the sentence.
Singular subjects require singular verbs.

Key Concept

Subject-Verb Agreement
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Topics

Subject-Verb Agreement

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