Question

Use suitable verb to fill in the blank:

This door is a fire exit. You ________ block it.

• A. shouldn't
• B. couldn't
• C. mustn't
• D. can't

Answer 1

Answer: (C)

The correct answer is Option B.

MUSTN'T is the negation of MUST.

MUST expresses compulsion.

In the given sentence, it is compulsory to not block the door because it is a fire exit.

Thus MUSTN'T is the correct answer.

The remaining options are incorrect because:

SHOULDN'T is the negation of SHOULD. It expresses obligation.

CAN'T is the negation of CAN. It expresses ability.

COULDN'T is the past tense of CAN'T.