题目

65. They are living in a        place and their houses are flooded almost once every year.  A. lie-low               B. low-lie                 C. low-lain               D. low-lying 答案：D下列说法中正确的是：（    ） A．力对物体不做功，物体的位移一定为零 B．静摩擦力总是做正功，滑动摩擦力总是做负功 C．作用力做功，反作用力不一定做功 D．一对平衡力所做的功的代数和总为零