Because of friction? A. energy is not always conserved B. not all potential energy is converted to kinetic energy
C. all an object's kinetic energy turns into potential energy
D all of an object's potential energy turns into kinetic energy

i think its B.NOT all potential energy is converted to kinetic energy

Maybe,  B. Not all potential energy is converted to kinetic energy.

Explanation:

Even if air resistance slows down the ball, the potential energy is the same. But if air resistance is in the way, not all of the potential energy can be converted to kinetic energy. Some of the energy has to be used to push the air molecules out of the way.

a is the best answer your welcome