从所给的A、B、C、D四个选项中选出最佳选项。

　　The Internet has become an important part of teenage life．Most of them use the Internet to get lots of knowledge and 　　1　　．The teenagers keep in touch with their friends online．It's 　　2　　 than phoning someone far away and e-mail is 　　3　　 much quicker than ordinary mail．

　　But some teenagers are not using it 　　4　　 the right way．Some of them would find life difficult without it．Some teenagers spend 　　5　　 time online．Some of the students who used to do well at school are now failing in exams because now they spend most of their 　　6　　 playing games online．

　　It is 　　7　　 for teenagers to use the Internet properly．They should learn 　　8　　 to use the Internet for study and keep away from 　　9　　 websites．They should make sure that surfing the Net doesn't 　　10　　 their homework or being with their friends．

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