Tie a small iron block in the middle of the rubber band and let the rubber band pass through both ends of the tin can. Why are you rolling on a gentle slope?

When the tin can rolls down on a slope that is not too steep, it rolls down from the highest point, from slow to fast, from fast to slow, and then to the lowest point. In the last stage of rolling, the gravitational potential energy decreases, while the kinetic energy of tin cans and the elastic potential energy of rubber bands increase. In the next stage of rolling, the gravitational potential energy and kinetic energy of tin will decrease, and the elastic potential energy of rubber band will increase; Finally, the tin can rolls from the highest point to the lowest point on the inclined plane, mainly because the gravitational potential energy is converted into elastic potential energy.

The tin can automatically rolls up from the bottom of the inclined plane, that is, when it rolls down from the lowest point, the tin can first rolls from slow to fast, and then from fast to slow to the highest point. In the next rolling process, the elastic potential energy of the rubber band decreases, while the kinetic energy and gravitational potential energy of tin increase. In the final stage of rolling, the elastic potential energy of rubber band and the kinetic energy of tin can be reduced, while the gravitational potential energy is increased. The tin can rolls from the lowest point to the highest point on the inclined plane, mainly because the elastic potential energy is converted into gravitational potential energy.

So choose D.