Answer:
The sentence that uses passive voice is sentence C.
Step-by-step explanation:
In most English sentences with an action verb, the subject perfoms the action denoted by the verb. As the subject does or acts upon the verb, the sentences are said to be in the active voice. However, you can change the normal order of words so that the subject is no longer active, but being acted upon by the verb. In this case, "the students" are not the ones doing the action but the ones receiving it, they are the ones "being instructed". In order to form a passive construction, you should move the active sentence's d.o to the subject position, place the active's sentence subject into a by-phrase, and add a form of auxiliary verb to be to the main verb and change the main verb's form.