问题 单项选择题

IP 数据报的报文格式如下图所示。在没有选项和填充的情况下,报头长度域的值为[*]

A.3

B.5

C.10

D.20

答案

参考答案:B

解析:IP报头中有两个表示长度的域,一个为报头长度,一个总长度。数据报在没有选项和填充的情况下,该值为“5”。

阅读理解

阅读理解。

     An old lady in a plane had a blanket(毯子)over her head and she did not want to take it off . The air

hostess spoke to her, but the old lady said, "I have never been  in a plane before , and I am frightened. I

am going to keep this blanket over my head until we are back on the ground again !"

     Then the captain came. He said, "Madam, I am the captain of this plane. The weather is fine, there

are no clouds in the sky, and everything is going very well. "But she continued to hide.

     So the captain turned and started to go back. Then the old  lady looked out from under the blanket

with one eye and said, "I am sorry, young man, but I don't like planes and I am never going to fly again.

But I'll say one thing, "She continued kindly, "You and your wife keep your plane very clean!"

1. An old lady had _________ .

A. glasses      

B. a blanket over her head        

C. a coat              

D. a basket

2. She didn't want to ________ .

A. take it off      

B. turn it off      

C. get on      

D. talk about it

3. _________ spoke to her .

A. The air hostess    

B. The man next to her    

C. her husband    

D. one of her friends

4. The old lady had never been _________ before .

A. abroad      

B. home      

C. in a plane      

D. in hospital

5. The woman didn't like planes and she was never going ________ .

A. to fly again      

B. to travel      

C. to go abroad      

D. to go home

填空题