问题 单项选择题

网线局域网中,802.11g使用的频率范围是______。

A.5.1~5.8GHz

B.2.4~2.485GHz

C.2.4~5.1GHz

D.2.485~5.1GHz

答案

参考答案:B

解析:本题目主要考查了“IEEE 802.11”这一知识点。
802.11a使用的频率范围5.1~5.8GHz,数据率最高为54Mbps,对于一定的功率级别而言传输距离较短;
802.11b无线LAN具有11Mbps的数量率,使用的频率范围2.4~2.485GHz,与2.4GHz电话和微波炉争用频谱;
802.11g使用的频率范围2.4~2.485GHz。并且与802.11b向后兼容,并具有与802.11a相同的高传输率54Mbps,使得用户能够更好的享受网络服务。

完形填空

阅读短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余项。

     小题1:    

With the invention of the Internet several decades ago, do you feel that since then it has made us human beings feel more connected to the world and one another, or has it isolated(使孤立)us and made us feel more alone than ever before?

What about you as an individual?

 小题2:The Internet enables us to know what’s happening in the world. We couldn't imagine talking to people everywhere in the world twenty years ago.

●小题3: It unites us because we talk to others from all around our country and tha world, but the Internet can be addicting, and keep us away from people for a while, There is an inherent (内在的) human need for direct human contact (e.g. touching, talking face to face, etc.) that the Internet has all taken away.

 小题4: It has given me freedom beyond my imagination. I’m home-bound with many duties to attend to. My life is a bit too crowded. Duties duties duties. I get lost many times not knowing who I really am!This medium is my best friend. It just lets me BE!I can speak here without fear or favour.

 小题5: Chatting online is completely different from hanging out with friends outside or hearing their voice over the phone.I find that it’s not just the Internet that has increased this sense of isolation,even iPods,MP3s,such devices kind of separate us,make us lose focus on the everyday happenings of life.

A.I think that the Internet isolates as well as unites us.

B.I believe it unites us more than it isolates us.

C.Do you feel that the Internet unites us or isolates us?

D.What is happening in the world today? E. The Internet is playing a more and more important role.

F. I think it has isolated us more.

G. I am truly grateful for this new technology.

判断题