Select the most appropriate option that can substitute the highlighted segment in the given sentence.
If it will rain tomorrow, I will be on leave.

Correct option is D

The correct substitution of the highlighted segment is (d) "it rains tomorrow." The conditional 'if' in English does not typically use the future tense but rather the simple present to express a condition. Thus, "it rains tomorrow" is the correct form to use in this conditional sentence. Grammatical rule used: In conditional sentences, the present simple tense is used to discuss future events that may occur.
General formula: If + Simple present, simple future
Example: If it rains tomorrow, we will cancel the picnic.