下列句子组成语段顺序排列正确的一项是（ ）
①但是人类错了，大自然在某个清晨突然咆哮，于是水和空气的污染，臭氧层破坏，阳光越来越凶猛地照射，都成了人类必须面临的严峻困境。
②也许是人类的天性，凡是无偿获得的东西，就不为自己所珍视。
③当原本无偿的东西开始收费以后，人类才珍视它们。
④我们曾以为大自然恣肆汪洋，可以无限攫取。
⑤人类肮脏了那些洁净的物质，于是有了装在瓶子里的蒸馏水和氧气罐头等等商品。
A：②④①⑤③
B：②⑤④③①
C：④③②①⑤
D：④⑤①③②
一个圆的直径是10cm，另一个圆的面积比这个圆的面积少16πcm2，则另一个圆的半径长为 ____m．
One day, in an English class, the students are doing their lessons. Their teacher, a young woman, is very happy. She sings with them and then she goes to the blackboard and writes “SMILES” on it. “This is the longest word in English,” she says to the class. A girl stands up and says, “It has only six letters. How can it be the longest word in English?” The teacher smiles and says, “Oh, look! There is a mile (英里) between the first letter and the last one.”
有A、B、C三个带电小球，如果小球A带正电，小球C吸引小球B，小球B排斥小球A，那么小球B带____电；小球C带____电．（填“正”或“负”）．
