Fill in the blank with a suitable verb:
_________ run if you feel tired.
A verb is used to express an occurrence, action, or state. It is the grammatical centre of the predicate in a sentence.
An auxiliary verb is a verb which gives is used in the formation of tenses, moods, tones, etc.
Option B is correct as if and run indicate the use of not and do respectively.
The other options are wrong as no other tense can be used here.
The correct answer is B) don't