题目

Bill and his family has been living in the six－family building for years. All the neighbors got along fairly well with each other until recently. An old man and his wife used to live on the second floor. Bill’s mother and the old lady were good friends. Unfortunately the lady died last month. Her husband could not live alone, so he had his grandson move over and live with him. The grandson has become a problem to all the neighbors, especially to Bill’s family. The walls of the building are thin and he is noisy. Bill is used to peace and quiet but the young man likes to listen to 如图所示，小明在玩蹦蹦杆，在小明将蹦蹦杆中的弹簧向下压缩的过程中，小明的重力势能、弹簧的弹性势能的变化是（ ）A．重力势能减小，弹性势能增大B．重力势能增大，弹性势能增大C．重力势能减小，弹性势能减小D．重力势能增大，弹性势能减小