Answer:
Person above me is right, it's B: microwaves, visible light, X-rays, gamma rays
Explanation:
A snowball picks up speed as it rolls down the mountain.<em> (D)</em>
Since the description includes acceleration ("picks up speed"), we know that the forces on the snowball must be unbalanced.
Strange as it may seem, I don't think ANY of those choices will work. Anybody else ?