题目

You probably know you should say “please” and “thank you” at restaurants. You probably know the rules of a library. You know you should respect(尊重) and be nice to your classmates. But do you have music manners? Keep It Down! You have to notice the volume of your music. You should not play your music so loud that everyone around you can hear it. Some people might even get angry. Usually, when you play the music loud on an MP3 player, other people can't hear the words of the song. They just hear a loud sound. No one wants to listen to this. Very loud music can also be bad for your ea下列对聚丙烯的描述中，有错误的是（    ） A.聚丙烯的分子长链是C—C链连接而成的          B.聚丙烯分子的长链上有支链C.聚丙烯每个链节上有3个碳原子                      D.聚丙烯能使溴水褪色