What is the best definition of a passive verb?
A. With a passive verb, the subject receives the action.
B. With a passive verb, the subject performs the action.
C. With a passive verb, the action is slow-moving.
D. Passive verbs indicate lazy subjects.

"A" is the answer. It's passive because the subject is not doing anything, it's being done to.

The answer is A.

Active sentence: Dave ate the doughnut. (Subject: Dave)

Passive sentence: The doughnut was eaten by Dave. (Subject: the doughnut)

A passive verb is a verb that is pretty easy-going doesn't let do many things bother it. Passive verbs see the glass as half full but they'd still be fine even if was half empty.

On the other hand aggressive verbs get angry at just about anything.

The subject of a passive sentence is still the main character of the sentence, but something else is performing the action: "I was thrown [by the horse]." So the answer is A.