Question

Fill in the blank with the most appropriate option:
“Where is he?”
“He ___ be walking in the park.”
A) can’t
B) is able to
C) has to
D) must

Answer 1

Hint: In the given question, we have to identify the appropriate option with regards to the context of the sentence. The speaker is trying to find the person for which he is having notion that the person is walking in the park. We will have to choose the correct modal verb for it.

A modal verb is a verb that expresses modality, such as likelihood, ability, permission, request, capacity, suggestions, order, obligation, or advice. Modal verbs are always used in conjunction with the base form of another semantic verb.

Complete answer:
We can understand the given question easily if we think of it as a conversation between two people. We have to complete the conversation by finding out the correct word.
Let us evaluate the options:
Option A) can’t – This option is incorrect because “can’t” will be used when the speaker is certain about the impossibility of the event. It is not impossible for the person to walk in the park. Hence, we cannot use “can’t”.
Option B) is able to – This option is incorrect because “is able to be walking in the park” is grammatically incorrect and improper. The present continuous form “walking” cannot be used with “is able to be”.
Option C) has to – This option is incorrect because “has to be walking in the park” indicates possibility whereas the speaker is speaking with certainty and confidence.
Option D) must – This option is correct because “must” is used to express a certain fact or an idea. In the given sentence, the speaker is certain that person is walking in the park. Thus, “must” is the correct answer.

Hence option D is correct. “He must be walking in the park.” Is the correct answer.

Note: We have to pay attention to the tense of the sentence also to identify the appropriate word. The given sentence is in the present tense and “must” can only be used for reference in the present and future. If the past is involved then we use “had to”.