A:一样大
B:A最大
C:B最大
D:C最大
(Ⅰ)求证:FG∥面ADD1A1;
(Ⅱ)求二面角B﹣EF﹣C的余弦值.
— ________ do you go to school?
—I often go to school ________ 7:30 am.