Which of the following sentences uses active voice?
a) yesterday's lecture was given by a guest speaker
b) the lecture was given by a guest speaker yesterday.
c) a guest speaker presented yesterday's lecture.
d) yesterday, a lecture was presented by a guest speaker.

A guest speaker presented yesterday's lecture – uses active voice .

C

Explanation

An active voice can be identified if the noun or the subject of the sentence makes an action or verb on the object.

Whereas in a passive voice, the object had made action or verb upon the subject or noun of the sentence.

These are taken in accordance with subject-verb agreement.

In most sentences, passive voice can be easily found out by the presence of the word ‘by’.

Among all the above options except C, each sentence uses the word ‘by’.

the answer is:

when will (v) the books (n) be (v) due?

nouns refer to people (other than pronouns), places and things, whereas verbs describe actions and are usually part of the predicate of a sentence. finally, pronouns can work as nouns and identify the participants in speech.

in the example sentence, "will" is a verb part or auxiliary verb, "be" is an infinitive verb and "books" is a plural noun.