Question

Fill in the blank with a suitable modal:
Your clothes smell and you've got a cough. You ________ smoke.

• A. don't have to
• B. should
• C. shouldn't
• D. have to

Answer 1

Answer: (C)

shouldn't

Answer : C

Modal verbs are auxiliary verbs that are used to express necessity or possibility.

Let's take a look at the usage of the modal verbs in the options:

• don't have to : It is the negative form of 'have to'
  
• should : It is used for expressing an opinion / advice / expectation / criticism about some past action or it can be used to ask for an advice
• shouldn't : It is the contracted form of 'should not'; it is the negative form of the modal verb 'should'
• have to : It is used for expressing an external obligation in positive sentences & removing an external obligation in the negative sentences

Here in the question, the speaker is trying to express an advice, that is to not smoke.

• As it is an advice & not an external obligation or rule or compulsion -- 'don't have to' is not suitable to complete the sentence here.
• 'should' is used to express an advice but in positive sentences. Here, ideally, the speaker would advice 'NOT TO' smoke (negative sentence).
• As it is an advice & not an external obligation or rule or compulsion -- 'have to' is not suitable here, also 'have to' is in positive sentences & not in negative sentence.

Therefore from among the options, 'shouldn't' is the most suitable verb to complete the sentence.

Thus, the correct complete sentence is:

Your clothes smell and you've got a cough. You SHOULDN'T smoke.