From the words or group of words lettered A to D, choose the word or group of words that best completes each of the following sentences:
The children's toys have all been stolen.
The correct answer is children's. Children is the plural of child. The same applies to women's; people's; men's. You would never write, “The childs' toy”, as “child” is singular, so the apostrophe would come before the s, “the child's toy”.