The correct response is:
The potential energy is increasing at point C because the bicyclist is increasing in elevation at that point.
Potential energy in a gravitational field is related to the height of an object above a reference point. As the bicyclist moves to a higher elevation, their potential energy increases. Points A and B are not correct responses for increasing potential energy if they are lower in elevation compared to point C. Moving forward does not affect potential energy directly; it is the change in height that matters.