Modals & auxiliaries MCQ — 14 Practice Questions with Answers

Explanation

Must not and need not are often confused because both contain not, but they function differently. Must not indicates prohibition: You must not disclose the file means disclosure is forbidden. Need not indicates lack of obligation: You need not disclose the file means disclosure is not required. Therefore the assertion is true, and the reason states the exact semantic difference that makes it true. The correct answer is that both are true and R explains A.

Explanation

Can't have plus past participle expresses an inferred impossibility about the past, so sentence 1 matches D. Shall, especially in formal notices, can express an assurance or promise, so sentence 2 matches C. Would not can show refusal or unwillingness in a past situation, which fits sentence 3 and B. May I is a standard polite request for permission, so sentence 4 matches A. The complete matching is therefore 1-D, 2-C, 3-B, 4-A.

Explanation

The required structure for a past duty that was not performed is should have plus the past participle, or ought to have plus the past participle. The clue is unfulfilled obligation in the past: the agenda ought to have been circulated, but it was not. Option A uses should have circulated, so it captures both the duty and the failure. Option B is only present advice; option C is an inference; option D is grammatically incomplete because ought needs to.

Explanation

The sentence tests the special auxiliary use of 'need'. In formal negative and interrogative contexts, 'need' can behave like a modal: it is followed by the bare infinitive, has no third-person -s, and forms questions without 'do'. Therefore 'Need we detain the witnesses?' is grammatical. If 'need' were used as an ordinary verb, the form would be 'Do we need to detain...?' The reason accurately states the rule behind the assertion.

Explanation

Used to covers both repeated past actions and past states that are no longer true: She used to own a house. Would can describe repeated past actions, especially with a time frame: She would visit the fort every winter. It is not normally used for stative verbs in this sense. Own is stative, so She would own a house near the fort is not a normal replacement for used to.