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 A is correct as the sentence is in the passive voice and it talks about a fact.

 The other options are wrong as no other tense can be used here.

The correct answer is A) are told