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Question

Difficulty: MediumVerb Tense, Aspect, and Mood

In 1977, oceanographers first discovered hydrothermal vents on the deep ocean floor, revealing complex ecosystems that thrive in complete darkness. Because these communities depend on chemosynthesis rather than photosynthesis, researchers ______ numerous expeditions since the initial discovery to study how these specialized organisms survive on chemical energy alone.

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

  1. A
    conducted
  2. B
    conduct
  3. have conductedAnswer
  4. D
    will conduct

Answer

The correct answer is 'have conducted'.
The correct answer uses the present perfect tense 'have conducted' to correctly match the temporal framework established by the prepositional phrase 'since the initial discovery.' This phrase indicates an action that began in the past and continues to have relevance or occur up to the present moment, which is the primary function of the present perfect aspect.

Step-by-Step Solution

1
Identify the subject and temporal clues in the sentence.
The plural subject is 'researchers'. The key temporal clue is 'since the initial discovery', which points to a time period starting in the past (1977) and continuing to the present.
Establishing the timeframe of the sentence is necessary to choose the correct verb tense and aspect.
2
Select the verb form that corresponds to this timeframe.
The present perfect tense ('have conducted') is used for actions that began in the past and continue to the present or have occurred repeatedly during a timeframe that includes the present.
This aligns with the grammatical function of 'since', which requires a perfect aspect verb.

Key Concept

Using the present perfect tense to express an action that began in the past and continues to the present, especially when cued by the word 'since'.
Estimated Time:1m 0s
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Topics

Verb Tense, Aspect, and Mood

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