“神舟五号”的成功发射与回收，表明我国的载人航天技术已经进入世界领先水平。在飞船的火箭推进器中常装有液态肼（用X表示）和过氧化氢（H₂O₂），它们混合时的反应方程式为：2H₂O₂＋X＝N₂↑＋4H₂O，则肼（X）的化学式为（    ）

   This is my beautiful home. There is a small garden in front of my house. There are many beautiful flowers in the garden. Behind my house there is a big tree. Near the tree, you can see a garage. My father’s beautiful car is in it now.
   On the first floor, there is a large living room, a dining room, a kitchen and a bathroom. I like watching TV in the living room. On the second floor, there is a small study room and two bedrooms. I love playing with the computer in my study. 
   What a nice home! I like it very much.

把边长为1的正方形ABCD沿对角线BD折起，使得平面ABD⊥平面CBD，形成三棱锥C﹣ABD的正视图与俯视图如图所示，则侧视图的面积为（　　）

①我国地域广阔，区域发展不平衡   ②我国发展成就举世瞩目，已成为发达国家

③我国资源总量大，人均资源充足   ④我国人口众多，人口、资源、环境矛盾突出