题目

Moral science is taught as a subject in most schools but with little effect. Perhaps part of the problem lies in the fact that morality is not a science, strictly speaking. It is too much of a social phenomenon, and also has too much of the personal and subjective things mixed within. Besides, morality itself changes with generations. So it is impossible to be defined in a textbook. I remember sitting through forty minutes of moral lessons, which told stories about little children who never told lies and were rewarded for their goodness. It had little effect and left no impression on 下列各种电器中，利用电流热效应工作的是（　　）A．电动机B．电冰箱C．电饭锅D．电风扇