题目

垫传排球是中考体育项目之一，向上传出的排球在_____的作用下又落回地面，该力的施力物体是_____。 答案：【答案】重力 地球 【解析】在地球附近的物体都会受到地球的重力，向上传出的排球最终会落回地面，就是因为排球始终受到竖直向下的重力作用；重力是由于地球的吸引而产生的，所以重力的施力物体是地球。--I'm told that John had another car accident this morning.      --I believe not. He  _________so careless.   A. shouldn't have been          B. wouldn't have been   C. couldn't have been           D. mustn't have been