What two objects have stored energy? A. ball rolling on the ground B. a small rock sitting on top of a big rock C. a stretched rubber band D. a stone lying on the ground

C and as other have expained below, B as well

Potential energy basically means something has the possibilty to change. A stretched rubber band could be released at any moment, which would then create kinetic energy. If the band wasn't stretched it wouldn't have any potential energy.