Explain why you agree or disagree that works of fiction should serve as “useful vehicles of a sound morality.”
I'm unfamiliar with the meaning of all the words in that question. I don't know what you mean by "sound" or even "morality." But I think there's a bit of an exaggeration in what literature can accomplish, what "moral lesson" it can give us. In fact, I often find it rather snobbish. It can have an attitude that says: "Behold my story. Only the most clever will be able to grasp its grave moral message. The rest of you can clean my car." That's not to offend any literature buffs, but I think it's best just to say what you mean, and mean what you say than to have sophisticated indirect forms of telling someone what you would tell them face-to-face if you were able.