Question

Fill in the blank with a suitable modal:
"I've had a terrible toothache for weeks."
"You _______ go to the dentist."

• A. ought
• B. would
• C. shouldn't
• D. should

Answer 1

The correct option is D should

Answer : D

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:

• ought : 'ought' is a synonym for 'should'; It is more formal than 'should' and is less commonly used, particularly in the question form
• would : It is used to make either a polite request or make a polite expression; also it is used to refer to a habitual action in the past
• shouldn't : It is the contracted form of 'should not'; it is the negative form of the modal verb 'should'
• 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

Here in the question, we see that the speaker is expressing an advice to go to the dentist.

Therefore from among the options, 'should' is the most suitable verb to complete the sentence, as it is used to express an advice. And also it is used in the construction of positive sentences.

• "ought" can be used to express an advice, but it is used in formal scenarios more than it is in informal scenarios, also it is used as "ought to", it would be incorrect to use only "ought".
• As it is an advice & NOT a request -- "would" is NOT suitable here.
• "shouldn't" is used to make an advice but it is used to construct negative sentences and NOT positive, thus it is NOT suitable here.

Thus, the correct complete sentence is:

"You SHOULD go to the dentist."