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Difficulty: MediumModal Auxiliaries and Expressing Modality

Given the strict security protocols at the international summit, all delegate credentials __________ verified by the chief security officer before admission was granted. Which option correctly completes the sentence?

  1. had to beAnswer
  2. B
    must to be
  3. C
    might can be
  4. D
    oughted to be

Answer

The correct option is 'had to be', which appropriately expresses past obligation or necessity.
The verb phrase 'had to be' correctly functions as the past tense expression of necessity and obligation, matching the past context set by 'was granted'.

Step-by-Step Solution

1
Analyze the time frame of the sentence.
The verb 'was granted' indicates that the action took place in the past.
Modal selection must align grammatically with past temporal markers.
2
Determine the required modality expressed by the context.
The context ('strict security protocols') requires expressing past necessity or obligation.
Because 'must' has no past tense form in English, 'had to' is used to express past necessity.
3
Evaluate the grammatical validity of each option.
'Had to be' is grammatically correct, while the other options contain structural errors such as double modals or invalid inflections.
Modal verbs cannot take infinitival 'to' markers directly, undergo regular past tense inflection, or stack adjacently.

Key Concept

Expressing Past Obligation and Modal Auxiliary Constraints
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Topics

Modal Auxiliaries and Expressing Modality

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