What kind of energy does each phase of the pendulum represent

Position A and Position C = Potential energy

Position B = Kinetic energy

Explanation:

When pendulum moves to and fro about its mean position then the velocity of pendulum is maximum at its mean position or at its lowest position of path.

As it move away from its lowest position the velocity of pendulum keep on decreasing and at the end it comes to rest.

So at the extreme ends of the path the pendulum will come to rest so its kinetic energy is zero and all its energy will become potential energy.

So here we know that in the given figure position A and Position C is extreme positions and the energy of that position is potential energy.

While at the lowest position all its energy becomes kinetic energy

a straight line sloped

it is b. absorbs thermal energy