A pendulum bob is given some initial potential energy by raising it. Next it is released.

Compare this maximum potential energy with the energy the pendulum bob contains at the lowest part of its path.

A. It is equal to the heat energy produced as it fell.

B. It is equal to the kinetic energy at the bottom of the swing.

C. It is equal to the kinetic energy at the bottom of the swing plus the heat energy produced as it fell.

This is a slightly tricky one, but I believe the best answer is C.

The central concept to this question in physics is the "conservation of energy". Energy is always conserved, it is never lost, it simply is converted into other forms.

Initially the pendulum is at rest with potential energy due to gravity and height. When it is released, this potential energy is converted into kinetic energy as it accelerates. However it is true that as the pendulum moves through the air, this will produce an aerodynamic resistance and generate heat, slowing the pendulum down slightly. So the total potential energy at the beginning would be equal to the sum of the kinetic energy at maximum velocity (the lowest part of the swing) + losses due to friction. If this experiment occurred in a vacuum there would be no aerodynamic losses.

B, It is equal to the kinetic energy at the bottom of the swing I think.