题目

Mr Smith was a wealthy industrialist, but he was not satisfied with life. He did not sleep well and his food did not  21   with him. The situation lasted for some time. Finally, after a   22   of sleepless nights, he decided to consult his doctor. The doctor advised a change of  23  . “Go abroad,” he said, “But I’m not good at foreign languages,” said Mr Smith. “It doesn’t matter,” said the doctor. “It won’t   24   you to talk a little less. Go on a voyage. Take plenty of exercise. Try to reduce your weight,  25   rich food.”        Mr Smith went to下列关于物体所受静摩擦力的说法正确的是（　　）A．静摩擦力有最大值，说明静摩擦力的值在一定范围内是可变的B．静止物体受到的摩擦力一定是静摩擦力C．静摩擦力的方向可能与其运动方向相同D．运动的物体不可能受静摩擦力作用