某公司要在如图所示的五角星（∠A=∠D=∠H=∠G=∠E=36°，AB=AC=CE=EF=FG=GI=HI=HK=DK=DB）中，沿边每隔25厘米装一盏闪光灯，若BC=（$\sqrt{5}$﹣1）米，则需要安装闪光灯（　　）

近年来，某市建设了l20多座“漂流书亭”，投放书籍7万多册，用“带一本书来，换一本书走”的方式，让该市“满城书香”。这一举措旨在（    ）

占地球表面积71%的物质是 ____，化学式是 ____，所含元素是 ____

    I'm Lucy. I have a happy family. There are four people in my family. My birthday is on January 1st. It's New Year's Day, too. My family and I will have a big dinner on that day. I have a little brother. He is four years old. His birthday is in winter. It's very cold but we can make a snowman. My mother's birthday is in March. My father's birthday is in March，too. We can plant trees and fly kites.