From point W to point Z, the ball is B- Potential energy was transformed to kinetic energy. We know this because, at point W, the ball is in its potential form, it has the potential to roll but it has not yet started to. As we let the ball go, we turn that potential energy into kinetic energy, which is the energy that it has due to its motion.
I hope I've helped! :)
C. exocytosis (I have to use 20 characters to respond and "answer it well". Exo means out/outside and exocytosis is an active transport system where a cell uses energy to transport material, like protein or waste, from inside a cell to the outside.)