敬献“哈达”是藏族同胞对客人最普遍、最隆重的礼节；维吾尔族人接待见面，习惯把手按在胸部中央，把身体前倾30度或握手，并连声说：“您好”；等等。由此可以看出（  ）

   The Internet has become part of teenage life. There’s a report on 3,375 students aged from 10 to 18 in seven Chinese cities. It says that 38% of them believe they use the Internet often. While most of them get useful information and use the Internet to help in their studies, some are not using it in a good way. Many are playing online games too much. A few even visit Web sites they should not look at. Bad things can happen if young people spend too much time on the Internet.
   In order to help young people use the Internet in a good way, a textbook on good Internet behavior has started to be used in some Shanghai middle schools this term. It uses real examples to teach students all about good ways of using the Internet. Some students also make online friends. But if you are meeting a friend offline, let your parents know.
   Teachers and parents all think the book is a very good idea. It will teach students how to be a good person in the online world. It will be a guide for teens using the Internet and keep students away from bad sites.

依次填入下列各句横线处的词语，最恰当的一组是 (　 　)

①昨晚，湖北武当山突发大火，有着千年历史的玉真宫主殿________化为灰烬。

②在中国统一大势不断巩固与发展的过程中，博大精深、与时俱进的中华文化________起到了团结各族人民、促进国家统一的重要作用，________为合理化解统一道路上所遇到的各种矛盾提供了重要的智力资源。

③学好本民族的语言尚且要花许多气力，________学习另一种语言呢？

如图是一个由4个相同的长方体组成的立体图形，它的主视图是（　　）