A teacher is teaching her class about animals. She has a list of barnyard creatures on the board and is asking the children what foodstuffs can be derived from each. ""What does the pig give us?"" Several hands go up. ""Bacon."" ""Sausages."" She nods, points to the next. ""The chicken?"" ""Chicken."" ""Eggs."" And then she comes to the last animal. ""Finally, what does the cow give us?"" A single hand goes up. ""Homework.""