in a mechanical clock the swinging of a pendulum. causes the hands to move. The diagram shows the path of the pendulum as it swings. At which point in it's swing does the pendulum have the least gravitational potential energy?

Explanation :
We know that the kinetic energy is possessed due to motion and potential energy is possessed due to height.
When the bob of the pendulum releases, its potential energy converted into kinetic energy. Then after some time, the gravitational potential energy is converted into kinetic energy.
From the figure, it is clear that the pendulum has the least gravitational potential energy at point C.
Hence, this is the required solution.