Which sentence uses the active voice?

My research paper is being finished two days early.

My research paper was finished two days early.

I finished my research paper two days early.

I finished my research paper two days early.

Explanation:

The passive means that something is being done to the subject. Since in the first two sentences the subject is research paper, and something is being done to them passively, these first sentences are passive. However, in the third, "I" is the subject, and "I" is doing something to the research paper, which, in this sentence, is the predicate. Since the subject is actively doing something to the predicate, this sentence is active.