A:10
B:﹣10
C:40
D:﹣40
Yesterday afternoon, Lucy played _______basketball and Lily played _______ piano.
图中的小球受到了重力、绳子的拉力和墙壁的支持力作用。请在图中画出这三个力的示意图。(在答题卡相应的位置上画出原图并作答)