Fill in the blank with the most appropriate word.
A verb is used to express an occurrence, action, or state. It is the grammatical center of the predicate in a sentence.
An auxiliary verb is a verb which is used in the formation of tenses, moods, tones, etc.
Option A is correct the sentence indicates the use of simple present tense. Also, the subject is singular and the previous sentence suggests the need for using 'not'.
The other options are wrong as no other tense can be used here.
The correct answer is A) doesn't