C is the answer you are looking for. A common idea isn't a moral, the generalization is the Main Idea, but not quite the moral. The thought of the characters almost never have the moral in them. Therefore, C is your answer.
It isn't certain, but since the strap was usually made of goat-skin, it could have been a symbol of fertility. By striking the women (often on the wrists) with it, it was said to ensure fertility, easy childbirth, and good health for them.
