患者，男，40岁。腰酸痠软，眩晕耳鸣，精神萎靡，性功能减退，并有遗精，早泄。其病因是

A．劳力过度

B．房劳过度

C．劳神过度

D．劳心过度

E．安逸过度

GM cannot be used as an indicator of stability at all angles of inclination because（）.

A.M is not fixed at large angles

B.there is no M at large angles

C.G is not fixed at large angles

D.there is no G at large angles