题目

___ present, the biggest nature park ___ milu ___ in Chian is the Nanhaizi Milu Park , ____ is about 20 kilometres south of Beijing.    A. At, of, deer, that   B.At, for, deer, which   C.In, for, deer, which   D.At, with, deer, that 答案：B 解析: at present 意为: 目前, 此处 for意为: 为….;用which引导一个非限制性定语从句(不作that),其先行词是the Nanhaizi Milu Park如图，正方形ADEF与梯形ABCD所在的平面互相垂直，AD⊥CD，AB∥CD，AD=12CD=2，点M在线段EC上，（Ⅰ）求证：BF∥平面CDE；（Ⅱ）若AB=2，三棱锥M-BDE的体积为43，求二面角M-BD-E的余弦值．