Boy's Adult Question

One day, a young boy was puzzled by one question in a paper that the teacher gave him. The boy finally took the paper to the living room where both his parents were watching television.

He went up to them and asked "Ma and Pa, What do you mean by sex?"

Taken aback by this question, both the parents make the boy sit by their side and the dad said "it is time for you to know son". Then both the parents started to explain all about sex from A to Z.

Finally when they have finished, the boy looked even more puzzled asked them "OK Dad. But how do I write such a long story in this little space?

Saying this he handed his parents the application form that says : Sex M/F?