Answer :
I think the answer is A because the subject usually acts out the verb.That is active and the action been done to it is the passive voice.
Answer: A. The hungry housecat killed the small, grey mouse last Tuesday and left it on the doorstep.
With active voice the subject, in this case the housecat is doing the action. So with this sentence, the cat killed the mouse and then left it on the doorstep.
Passive voice sentences usually use the word was like in three of the four examples you gave.
In example B the following wording was used: was left, was killed (that is passive voice).
Example C: was left
Example D: was killed
While example C and D start off using active voice (the hungry housecat killed) it finishes using passive voice. The tenses should remain the same throughout the sentence.
Hopefully this helped and good luck