After doing homework problem #18, I realized that I still have trouble distinguishing between active and passive voices. If anyone else felt the same way, I hope this passage will help. According to CliffsStudySolver™ English Grammar, voice is the form of a verb that indicates whether the subject is doing the action of the verb or receiving the action of the verb. In active voice, the subject does the action of the verb.
Subject + verb + object. = Doer of action + verb + receiver of action.
Yun caught the ball.
Karen fixed the problem.
In passive voice, the active subject and direct object change places, and the subject receives the action of the verb.
Subject + verb by object. = Receiver of action + verb by doer of action.
The ball was caught by Yun.
The problem was fixed by Karen.