问题 单项选择题

在ISO/OSI参考模型中,网络层的主要功能是

A.提供可靠的端一端服务,透明地传送报文

B.路由选择、拥塞控制与网络互连

C.在通信实体之间传送以帧为单位的数据

D.数据格式变换、数据加密与解密、数据压缩与恢复

答案

参考答案:B

解析: ISO/OSI参考模型中,根据分而治之的原则将整个通信功能划分为物理层、数据链路层、网络层、传输层、会话层、表示层和应用层7个层次。网络层的功能是通过路由选择算法,为分组通过通信子网选择适当的路径。网络层要实现路由选择、拥塞控制和网络互联等功能。

阅读理解

阅读理解。

     Jack is six years old. He has no sisters. But he has a brother. His brother's name is Mike. Jack likes eating apples, oranges and bananas. Sometimes he eats some of his brother's apples. And his brother hits (打)him for that. He doesn't like Mike. This September he is going to school.It's the ninth day at school. Jack and his classmates are having a new lesson.

     "Jack, how much is five minus three, please?"

     "It's…it's…"

     "Now, listen to me," says the teacher, "If your sister has five apples, and you have eaten three of them…"

     "But I have no sisters." Jack says.

     "Oh, sorry. But do you have any brothers?"

     "Yes."

     "Now, if your brother has five apples, and you have eaten three of them, tell me how…?"

     "He'll certainly give me a good beating" Jack says quickly.

1. How many brothers and sisters does Jack have?

A. One brother and one sister.

B. One brother and two sisters.

C. Only one brother.

D. No brothers and no sisters.

2. Why does Mike sometimes hit Jack? Because _______.

A. Jack often hits Mike.

B. Jack doesn't like eating fruit

C. Jack doesn't do his homework

D. Jack often eats some of Mike's of apples

3. Why can't Jack answer his teacher's question? Because _______.

A. he has no sisters

B. he has no brothers

C. he doesn't understand his teacher's question

D. he has no apples

4. If you have five apples, you have eaten three of them, how many apples remain (剩下) _______.

A. two

B. three

C. four

D. one

5.When does the story happen (发生)?_______.

A. In October.

B. On the ninth day at school.

C. In a new lesson.

D. At school.

判断题