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Question

Difficulty: EasyVerb Tense, Aspect, and Mood

In 1928, Scottish researcher Alexander Fleming accidentally discovered penicillin, which became the world's first effective antibiotic. Since Fleming's historic breakthrough, medical researchers ______ countless other antibiotics to treat bacterial infections, saving millions of lives and fundamentally transforming modern healthcare.

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

  1. have developedAnswer
  2. B
    developed
  3. C
    had developed
  4. D
    will develop

Answer

The present perfect tense 'have developed' is correct because the word 'since' indicates an action that began in the past and continues to be relevant in the present.
The correct answer is the phrase 'have developed' because the sentence establishes a time frame starting in the past and extending to the present with the prepositional phrase 'Since Fleming's historic breakthrough'. This requires the present perfect tense. Because the subject 'medical researchers' is plural, the plural auxiliary verb 'have' must be used.

Step-by-Step Solution

1
Identify the subject and temporal markers in the sentence.
The subject is 'medical researchers' (plural) and the time marker is 'Since Fleming's historic breakthrough'.
This establishes that the verb must be plural and in a tense that connects a past point to the present.
2
Select the verb form that matches the temporal marker.
The present perfect plural verb 'have developed' is the correct choice.
Present perfect tense is required to show action starting in the past and continuing up to or affecting the present.

Key Concept

Using the present perfect tense with the time marker 'since'
Estimated Time:45s
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Topics

Verb Tense, Aspect, and Mood

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