Question

Choose an appropriate option to complete the sentence:
That restaurant _____ be very good. It's always full of people.

• A. can
• B. could
• C. may
• D. must

Answer 1

The correct option is D must

'Can' indicates ability / capacity.

'Could' indicates past ability / permission.

'May' indicates permission / possibility.

'Must' indicates certainty.
Here, it is implied that the restaurant is good based on the fact that it is always full of people. Hence, it is a certainty that the restaurant is good. Therefore, the correct option is D) must.