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PPP(Point-to-Point Protocol)是SLIP(Serial Line IP protocol)的继承者，它提供了跨过同步和异步电路实现路由器到路由器(router-to-router)和主机到网络(host-to-network)的连接。

CHAP(Challenge Handshake Authentication Protocol，挑战—握手验证协议)和PAP(Pass-word Authentication Protocol，口令验证协议)通常被用于在PPP封装的串行线路上提供安全陛认证。使用CHAP和PAP认证，每个路由器通过名字来识别，可以防止未经授权的访问。

路由器Router1和Router2的S0口均封装PPP协议，采用CHAP做认证，如图1所示。

设置如下：

Router1:

hostname router1

username router1 password xxx

interface Serial0

ip address 192.200.10.1 255.255.255.0

encapsulation ppp

clockrate 1000000

ppp authentication chap!

Router2:

hostname router2

username router2 password xxx

interface Seria10

ip address 192.200.10.2 255.255.255.0

encapsulation ppp

ppp authentication chap

 

解释配置中画线部分内容含义。

答案

参考答案：

Router1: hostname router1 //路由器名为muter1 username router2 password xxx //建立一用户，用户名为ronter2，口令为xxx interface Seria10 ip address192.200.10.1 255.255.255.0 encapsulation PPP //设置PPP封装 clockrate 1000000 PPP authentication chap //设置PPP认证方法为chap ! Router2: hostname roater2 usemame router1 password xxx interface Serial0 ip address 192.200.10.2 255.255.255.0 encapsulation PPP PPP authentication chap

单项选择题

Nuclear power’s danger to health, safety, and even life itself can be summed up in one word: radiation.

Nuclear radiation has a certain mystery about it, partly because it cannot be detected by human senses. It can’t be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can’t detect them, sense them, without a radio receiver. Similarly, we can’t sense radio activity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things.

At very high levels, radiation can kill an animal or human being outright by killing masses of cells in vital organs. But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not be significant. This is the case when only a few cells are hit. And if they are killed outright, your body will replace the dead cells with healthy ones. But if the few cells are only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in a deformed way. They can grow into cancer. Sometimes this does not show up for many years.

This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the victim being aware at the time that damage has occurred. A person can he irradiated and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or liable to serious illness as a result of radiation absorbed by its grandparents.

Radiation can hurt us. We must know the truth.

The word "significant" in Paragraph 3 most probably means（）

A. responsible

B. meaningful

C. fatal

D. harmful
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多项选择题

能够详细反映某一类经济业务增减变动的会计账簿是（）。

A.总分类账

B.明细分类账

C.备查账

D.序时账
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