题目

―I have lost the cellphone my brother bought me as my birthday present. How careless I was!―Bad luck! Then you have to buy         tomorrow         we are going shopping together in Kaiyuan Department Store.       A．it; that                 B．other; when         C．one; when           D．the other; which 答案：C(本小题满分12分) 为了绿化城市，准备在如图所示的区域内修建一个矩形PQRC的草坪，且PQ∥BC，RQ⊥BC,另外△AEF的内部有一文物保护区不能占用，经测量AB=100m，BC=80m，AE=30m，AF=20m． (1)求直线EF的方程； (2)应如何设计才能使草坪的占地面积最大？