如图，Rt△ABC中∠C=90°，∠BAC=30°，AB=8，以$2\sqrt{3}$为边长的正方形DEFG的一边GD在直线AB上，且点D与点A重合，现将正方形DEFG沿A﹣B的方向以每秒1个单位的速度匀速运动，当点D与点B重合时停止，则在这个运动过程中，正方形DEFG与△ABC的重合部分的面积S与运动时间t之间的函数关系图象大致是（　　）

如图的山脉和河流构成了我国一条重要的地理分界线，作为重要的地理分界线，该线南北地理差异很大，下列说法正确的是（　　）

    Singapore is not just a clean and tidy city in the world, it's also the greenest. There are (A) 三个原因why it is so.
Say "No" to waste
    Singaporeans do not waste a single drop of water. They recycle water and save( B ) almost all rainfall. The water can be used for industry （工业） and even drinking.
Many "green" buildings
    The Duke-NUS Graduate Medical School is one of the great examples of (C) pretty green design. It uses sustain-able design elements (可持续发展的设计元素) in its school building. ( D ) Singapore has many green buildings like this.
Get them while they're young
    The Green Singapore 2050 (GS2050) is a community platform (社区平台) for young people to express their great worries about environmental problems, and think of solutions for(E) them. Why 2050'？It's because these young people will be the ones to run the country in 2050, and hopefully they will solve the world's problems.

如图，棱长为4的正四面体ABCD，AE=$\frac{1}{3}$AB，试建立适当的坐标系，写出各点的坐标．

我市中小学大力提倡素质教育，取得了重大成果．老师对本学期全班50名同学所选择的活动项目进行了统计，根据收集的数据制作了下表：