题目

--- Do you know _____ there is a post office around here? --- Yes, it’s on the Second Street. A. where                    B. if                       C. that               D. which 答案：B如图，一架云梯长25 m，斜靠在一面墙上，梯子底端离墙7 m． (1)这个梯子的顶端距地面有多高? (2)如果梯子的顶端下滑4 m，那么梯子的底部在水平方向也滑动了4 m吗，请通过计算说明?   (本题4+5=9分)