题目

点P是等腰三角形ABC所在平面外一点,PA⊥平面ABC,PA=8,在△ABC中,底边BC=6,AB=5,则P到BC的距离为( ) A.          B.            C.          D. 答案：A 解析:作AD⊥BC于点D,连结PD,易证PD⊥BC,故PD的长即为P到BC的距离.Qian Xuesen is a great Chinese scientist ______ great contributions (贡献) to building our motherland. [     ]A. which has made B. which have made C. who has made D. who have made