问题 单项选择题

如果 IP 地址为 202.130.191.33,屏蔽码为 255.255.255.0,那么网络地址是_____。

A.202.130.0.0

B.202.0.0.0

C.202.130.191.33

D.202.130.191.0

答案

参考答案:D

解析:根据 IPv4 协议,IP 地址由 32 位二进制数构成,由点分十进制表示时,分为 4 段,每段由 8 位二进 制数构成。为了使网络的路由器知道要把数据报转到哪一个子网中,必须由一个码来确定子网号,这个码 就是屏蔽码,或者叫做掩码。屏蔽码(掩码)的作用是把 IP 地址中的子网主机号屏蔽掉,得出子网号。这就可以通过二进制数的按位“与”来实现。本题中,IP 地址为 202.130.191.33,屏蔽码为 255.255.255.0,即:IP 地址为:11001010,10000010,10111111,00100001屏蔽码为:11111111,11111111,11111111,00000000“与”的结果:11001010,10000010,10111111,00000000所以原来的主机号部分是:00000000,即 0,可知网络号为:202.130.191.0。

阅读理解

As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

Scientists have found out that the radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation won’t be found until their children even grandchildren are born. Some special medicine may work a little, but no really effective medicine has been found so far.

Space rubbish is also thought to be a great danger to spacemen. It’s reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space rubbish. An explosion(爆炸)in space in 1999 made a cloud of 300,000 fragments, each at least 4mm in size. A small piece of these even knocked a spaceship window and caused some damage(损坏).

Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish. Although space is really dangerous, it interests many people on the earth. In the near future, it may become possible for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should do something to help improve the space environment.

小题1: ______ shows the man-made things in space in the correct way.

   

A.

B.

C.

D.小题2:The radiation from the sun and other stars is ______ to spacemen.

A.good

B.helpful

C.useful

D.harmful小题3: The underlined word “fragments”means “______”.

A.碎片

B.泡沫

C.烟雾

D.飞碟小题4: The passage talks about _________ kinds of danger in space.

A.two

B.three

C.four

D.five小题5: Which of the following is TRUE?

A.Scientists have found out ways to solve any problem in space.

B.Every one of us can have a travel to space in ten years.

C.The harm of the radiation may be found in the spacemen’s children.

D.Space is really dangerous, so it doesn’t interest anyone on the earth.

问答题 简答题