问题 单项选择题

下面关于静态路由表说法中错误的是______。

A.是由人工方式建立的

B.在网络系统运行时,系统将自动运行动态路由选择协议

C.网络结构发生变化时,路由表无法自动地更新

D.需要网络管理人员将每一个目的地址的路径输入到路由表中

答案

参考答案:B

解析:路由器选择算法分为两类:静态路由表、动态路由表。静态路由表是由人工方式建立的,网络管理人员将每一个目的地址的路径输入到路由表中。网络结构发生变化时,路由表无法自动地更新。动态路由表,在网络系统运行时通过自动运行动态路由选择协议自动建立路由表。当Internet结构变化时,例如当某个路由器出现故障或某条链路中断时,动态路由选择协议就会自动更新所有路由器中的路由表。

选择题
阅读理解

There are three separate sources of danger in supplying energy by nuclear power(原子能).

First, the radioactive material must travel from its place of production to the power station. Although the power stations themselves are strongly built, the containers used for the transport of the materials are not. Normally, only two methods of transport are in use, namely road or rail. Unfortunately, both of these may have an effect on the general public, since they are sure to pass near, or even through, heavily populated areas.

Second, there is the problem of waste. All nuclear power stations produce wastes that in most cases will remain radioactive for thousands of years. It is impossible to make these wastes nonradioactive, and so they must be stored in one of the inconvenient ways that scientists have invented. For example, they may be buried under the ground, or dropped into deserted mines, or sunk in the sea. However, these methods do not solve the problem, since an earthquake could easily break the containers.

Third, there may occur the danger of a leak(泄漏) or an explosion at the power station. As with the other two dangers, this is not very likely, so it does not provide a serious objection to the nuclear program. However, it can happen.Separately, these three types of dangers are not a great cause for worry. Taken together, though, the probability of disaster(灾难) is extremely high.

1.Which of the following is FALSE?

A.It is possible that a leak or an explosion occurs at a power station.

B.It is unusual for radioactive materials to be transported across land.

C.The containers are likely to be broken by an earthquake.

D.Nuclear wastes remain dangerous in most cases for many years. 

2.The author thinks that the ways to store nuclear wastes are ________.

A.easy      B.impossible         C.reasonable        D.ineffective 

3.What do we learn from the last paragraph?

A.The power station is a safe place.

B.The dangers of nuclear energy can be prevented.

C.The general public are strongly against the nuclear program.

By itself, none of the three dangers is very likely to cause much worry.

4.What is this passage about?

A.Uses of nuclear power.          B.Dangers from nuclear power.        

C.Public anger at nuclear power.  D.Accidents caused by nuclear power.