问题 单项选择题

如下图所示一台路由器连接3个以太网,假设主机C上要发送一个IP分组,使得主机D和主机E都会接收它,而子网3和子网4上的主机都不会接收它,那么该IP分组的目标IP地址是______。

A.255.255.255.255
B.130.130.20.255
C.127.0.0.1
D.130.130.19.255

答案

参考答案:A

解析: 本题考查路由器的功能和IPv4地址的特点,主机D属于子网130.130.19.0,主机E属于130.130.20.0,分别属于不同的网络,可以同时接收的IP分组必定是广播报文,题目又要求该广播报文不能转发到子网3,和子网4,则这个广播报文必定是有限广播地址255.255.255.255,路由器可以割断广播报,因此答案是A。
(1)直接广播地址:当用户想向互联网中某个网络中所有主机发送数据报,叫直接广播,具有这种特点的地址叫直接广播地址。直接广播地址由一个有效的网络号和全“1”的主机号构成。
(2)有限广播地址:当用户想向本网中每一台主机发送数据报,叫有限广播。有限广播将广播限制在最小的范围内,又称为本地广播地址。有限广播地址为255.255.255.255。

选择题
阅读理解

阅读理解。

     Maurice Sendak's children's book, Where the Wild Things Are, published in 1963, has become

very successful throughout the years and was made into a movie earlier this year.

     The book's main character is a boy named Max who gets into trouble with his mother and is sent

to bed without any supper. Before long, Max's room magically becomes a forest, and he sails away

to a land where monsters(怪物,怪兽) live. Max isn't scared, though, and becomes king of the wild

things, but after a while, he begins feeling homesick. Max sails back home and his supper is still hot

when he arrives in his bedroom.

     Many teachers and professors like this story and use it to help children develop creativity and

imagination. Melina Davis, an education professor, said she likes how the book contains a couple

of pages that have only pictures on them. "This allows children to shape the story themselves," she

said.

     The book contains a few of larger words that some parents worry may confuse children, but

experts say those words help improve children's reading skills and challenge them.

     Davis said the book is well written which helps kids get involved in the story. "The book talks

about what all children go through, like 'I was naughty but my mommy still loves me'," Davis said.

The book also encourages children to face their fears. "I think it's really good to show that Max

makes friends with the monsters," Davis said. "Kids can find out monsters aren't always the thing

under the bed that's going to scare them. I think this is good because it shows that the children can

go to scary places but still have a positive experience."

     Since the book has been successful throughout the years, a movie was recently made and many

people are excited to see it. Davis said she thinks the movie will be wonderful but it might be a little

scary for younger children. "You don't want bad dreams over a book that's extremely wonderful,"

Davis said.

1. Teachers and professors like the book because it helps children ______.

A. understand pictures                      

B. improve reading skills

C. face their fear bravely                  

D. become more imaginative

2. Why does the book contain some larger words?

A. To make the story more formal.    

B. To help challenge the children's reading skills.

C. To encourage the children to learn more new words.          

D. To help children better understand the story.

3. Which of the following is TRUE according to the passage?

A. The character Max is brave enough in the story.        

B. Max was sent to the forest as punishment.

C. People of all ages are in favor of the book.            

D. The movie based on the book proves to be a great success.

4. What does Davis think of the movie?

A. She thinks children of all ages will love it.  

B. She encourages children to see it to fight against their fear.

C. She worries that it might be too frightening for some children.

D. She believes it will be a better choice for children than the book.

5. What's the author's purpose in writing the passage?

A. To advise parents to help children to improve their reading skills.        

B. To comment on a famous children's book.

C. To encourage children to face their fear and become more imaginative.        

D. To introduce a movie based on a children's book.