A French woman goes to London to see her son. She knows a little English, but can not speak it very well. One day she goes to a shop. She wants to buy a hen for supper. But she can not remember the English word for "hen". Just then the shop waiter asks her, "Can I help you?" "I want the egg's mother." the woman answered. The shop waiter does not understand her and says, "Sorry, we have not any bigger eggs." Suddenly the woman remembers the word "cock". "I want the cock's wife!" she says. This time the shop waiter laughs. The shop waiter thinks that an egg's mother must be  _  .
a bigger egg the cock's wife a hen the hen's sister