题目

When she was doing the cleaning yesterday, Mum found the ring that she _____ years ago. A. loses                               B. has lost             C. lost                                 D. had lost 答案：D 解析: 略（如图）甲、乙两楼相距20m，从乙楼底望甲楼顶的仰角为60°，从甲楼顶望乙楼顶的俯角为30°，则乙楼高为______m.