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Difficulty: MediumModal Auxiliaries and Expressing Modality

Read the scenario below:

'The main vault gates remained fully sealed without any physical sign of forced entry, yet the confidential documents inside had vanished. Investigators concluded that the culprit __________ possessed the administrative clearance code to open the digital lock.'

Which of the following modal auxiliary phrases correctly completes the sentence to express a past logical deduction based on available evidence?

  1. must haveAnswer
  2. B
    might can have
  3. C
    must to have
  4. D
    oughted to have

Answer

The phrase 'must have' is the correct choice because it appropriately expresses past logical certainty based on circumstantial evidence.
The phrase 'must have' is correct because 'must' + perfect infinitive ('have possessed') indicates a past deduction derived from strong logical evidence presented in the context.

Step-by-Step Solution

1
Analyze the semantic meaning required by the sentence context.
The sentence presents strong circumstantial evidence ('vault gates remained fully sealed', 'documents vanished') requiring a expression of high certainty/logical deduction regarding a past event.
Modal auxiliaries express different attitudes like deduction, obligation, permission, or ability depending on context.
2
Select the correct structure for past logical deduction.
The modal auxiliary 'must' paired with the auxiliary 'have' and a past participle ('must have possessed') forms the past deduction structure.
'Must + have + past participle' is the standard grammatical structure for past logical conclusions.
3
Eliminate ungrammatical auxiliary structures.
Discard forms containing double modals ('might can'), incorrect infinitive markers ('must to'), or invalid verb inflections ('oughted').
Modal verbs do not inflect with tense suffixes and cannot be stacked directly alongside other modal verbs.

Key Concept

Expressing past logical deduction using modal auxiliaries
Estimated Time:1m 0s
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Topics

Modal Auxiliaries and Expressing Modality

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