The mother hesitated, then quickly replied, "Um, they're making cakes."
The next day they were at a zoo and the little girl saw two monkeys having sex. Again she asked her mother, "What are they are doing?"
Her mother replied with the same response: "Making cakes."
The next day the girl said to her mother, "Mommy, you and Daddy were making cakes in the living room last night."
Shocked, the mother asked, "How do you know?"
She said, "Because I licked the icing off the sofa."