How do you know if you are a boy or a girl?

One way you could tell is put your back flat straight against a wall , put one foot directly in front of another while in the same position, mark your furthest leg's position from the wall, get a chair, not heavy, not too light, and put bend over to the wall, while the chair is in front of your toes, pick it up to your chest, now stand...

If you CAN stand while the chair is touching your chest, you are a girl.
If you CAN'T stand while the chair is touching your chest, you are a guy.