9) because of friction a) energy is not always conserved. b) not all potential energy is converted to kinetic energy. c) all of an object's kinetic energy turns into potential energy. d) all of an object's potential energy turns into kinetic energy.

The answer is: B) NOT all potential energy is converted to kinetic energy

Let's discard each option in order to find the correct option:

A) energy is NOT always conserved, False: Energy is always conserved, energy can turn to another kind of energy but the energy will be always conserved.

B) NOT all potential energy is converted to kinetic energy, True: We must remember that Energy of Friction usually opposes to the movement of a body, so, it means that all the potential energy (work) applied to an object would not be converted into kinetic energy (movement).

C) all of an object's kinetic energy turns into potential energy, false: Since the Energy of Friction is acting, not all of the kinetic energy will be turned into potential energy.

D) all of an object's potential energy turns into kinetic energy, false: Since B is true, D is false, not all potential energy is converted to kinetic energy because of the energy of friction.

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