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Difficulty: EasySubject-Verb Agreement

A recent ecological survey of the unique wetlands in southern Florida reveals that the primary threat to local biodiversity is not urban sprawl but invasive plant species. A single population of these fast-growing weeds, despite efforts by conservationists to manage their spread, ________ the delicate balance of the native ecosystem by outcompeting local flora for sunlight and soil nutrients.

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

  1. A
    disrupt
  2. disruptsAnswer
  3. C
    are disrupting
  4. D
    disrupting

Answer

The singular present-tense verb 'disrupts' is correct because it matches the grammatical number of the singular subject 'population'.
The singular verb 'disrupts' agrees with the singular noun 'population', which serves as the true subject of the clause. The plural nouns 'weeds' and 'conservationists' reside in intervening phrases and do not alter the singular grammatical number of the subject.

Step-by-Step Solution

1
Identify the grammatical subject of the verb in the target sentence.
The subject is the singular noun phrase 'A single population', not the plural nouns 'weeds' or 'conservationists' found within the intervening modifier and prepositional phrases.
Subject-verb agreement requires identifying the main noun performing the action, ignoring all intervening prepositional phrases or parenthetical information.
2
Select the verb form that matches the singular subject and maintains consistent tense.
The singular, present-tense verb 'disrupts' must be selected to match the singular subject 'population' and the present-tense context established by the verbs 'reveals' and 'is'.
The correct verb must agree in number (singular) with the subject and maintain a consistent temporal framework with the rest of the passage.

Key Concept

Subject-Verb Agreement with Intervening Phrases
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Topics

Subject-Verb Agreement

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