A. B. C. D.
(Ⅰ)求椭圆C的方程;
(Ⅱ)过点B(1,0)且斜率为k1(k1≠0)的直线l于椭圆C相交于E,F两点,直线AE,AF分别交直线x=3于M,N两点,线段MN的中点为P,记直线PB的斜率为k2,求证:k1•k2为定值.
①充满……____ ②迟到____
③到……时候____ ④(闹钟)闹响____
⑤忘记去做某事____ ⑥忘记已做了某事____
— did you stay in the library?
— I stayed there for over two hours.