You Stand with Your Heels Against a Wall and Bend

You stand with your heels against a wall and bend ninety degrees forward at the waist.

A) You fall forward because your center of gravity moves ahead of your base of support.
B) You fall forward because of the momentum you gain when you move.
C) You are able to maintain your balance.
D) You fall forward because the muscles in your feet aren't strong enough to stop you.