Question

there are some black clouds in the sky it ______ rain this evening (a) must (b) may (c) ought to ​

Answer 1

There are some black clouds in the sky it may rain this evening.

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Answer 2

Answer:

there are some black clouds in the sky it may rain this evening.

The word may is an auxiliary word which is used to frame proper sentences. These are also called as Helping Verbs. This verbs acts as the main verbs during the absence of main verbs.

The above sentence is a simple future tense. The structure of simple present tense is sub + V1 + will/shall/may + object.

There is a possibility of raining so there must be usage of may to express the possibility.

Hence, the answer is may.