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Question

Difficulty: HardModal Auxiliaries and Expressing Modality

Complete the sentence below by supplying the modal verb phrase that correctly expresses past logical impossibility.

Answer:Considering that the chief archivist was under constant security surveillance throughout the evening, she 【could not have removed】 the classified manuscript without being detected on camera.

Answer

could not have removed
The modal phrase 'could not have removed' (or 'cannot have removed') correctly expresses a logical deduction of past impossibility based on the contextual evidence of continuous surveillance.

Step-by-Step Solution

1
Analyze the sentence context and temporal clues.
The contextual phrase 'under constant security surveillance throughout the evening' provides factual evidence regarding a completed past situation.
Determining whether a sentence requires present modality or past modal deduction depends on time indicators and factual context.
2
Identify the specific modal meaning required.
The sentence calls for an expression of past logical impossibility—deducing that an action was impossible given the circumstances.
Modal auxiliaries express semantic nuances such as obligation, permission, logical deduction, and impossibility.
3
Formulate the correct modal structure.
The structure 'could not have + past participle' (or 'cannot have + past participle') correctly conveys negative past deduction/impossibility.
Using simple past modals without the perfective auxiliary 'have' fails to establish the deduction relative to a finished past event.

Key Concept

Modal Auxiliaries for Past Logical Impossibility
Estimated Time:1m 30s
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Topics

Modal Auxiliaries and Expressing Modality

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