题目

Hank Viscardi was born without legs. He had not legs but stumps(残肢)that could he fitted with a kind of special boots. People stared at him with cruel interest. Children laughed at him and called him ‘Ape Man’ (猿人) because his arms practically dragged on the ground. Hank went to school like other boys. His grades were good and he needed only eight years to finish his schooling instead of the usual twelve. After graduating from school, he worked his way through college. He swept floors, waited on table, or worked in one of the college offices. During all this busy life, he h运动员跳高时从离开地面到上升到最大高度的过程中（ ）A．动能转化为重力势能B．重力势能转化为动能C．弹性势能转化为机械能D．重力势能减小，动能增大