Question

Choose the option to fill in the blanks. People _______ walk on the grass in the park.
A.need not
B.may not
C.could not
D.must not

Answer 1

To answer this question we need to understand the context of the sentence.

In a park grass is well kept and maintained.

It is expected that everyone who comes to the park should leave it as they found it.

Stepping on the grass destroys the grass.

Therefore it is an instruction that nobody should step on the grass.

The conjunction that expresses instruction and obligation is must.

Therefore the correct answer is :

MUST NOT

Answer 2

We have been given a fill in the blanks. We need to fill the blank with a correct answer.

The question given to us is.

People _______ walk on the grass in the park.

The answer to the question is. D) People MUST NOT  walk on the grass in the park.