The best answer that describes the energy changes during Rebecca's time on the slide is:
potential → kinetic → potential
Here's why: When Rebecca is at the top of the ladder, she has potential energy due to her height. As she slides down, that potential energy is converted into kinetic energy as she gains speed. Upon entering the pool, her kinetic energy decreases and can be transformed back into potential energy as she floats in the water (depending on how deep she goes).