How many times _________ told you not to waste your time?

How many times _________ told you not to waste your time?

Explanation

 "Your teachers have"is the correct construction.

"Have" agrees with the plural subject "teachers" and indicates the past tense.



"(B) haven't your teachers" is incorrect because it's in the present perfect tense. The sentence is asking about something that happened in the past, not the present.

"(C) your teacher have" is incorrect. "Your teacher" is singular, so "has" should be used.