问题 单项选择题

如果子网掩码是255.255.192.0,那么以下主机______必须通过路由器才能与主机147.69.144.16通信。

A.147.69.127.224
B.147.69.130.33
C.147.69.148.129
D.147.69.191.21

答案

参考答案:A

解析: 子网掩码是一个应用于TCP/IP网络的32位二进制值,它可以屏蔽掉IP地址中的一部分,从而分离出IP地址中的网络部分与主机部分。
子网掩码为255.255.192.0的二进制表示形式为: 11111111 11111111 11000000 00000000
主机地址147.69.144.16的二进制表示形式为: 10010011 01000101 10010000 00010000
主机地址147.69.127.224的二进制表示形式为: 10010011 01000101 01111111 11100000
主机地址147.69.130.33的二进制表示形式为: 10010011 01000101 10000010 00100001
主机地址147.69.148.129的二进制表示形式为: 10010011 01000101 10010100 10000001
主机地址147.69.191.21的二进制表示形式为: 10010011 01000101 10111111 00010101
由以上分析可知,在本试题所给出的4个B类网络地址中,主机地址147.69.130.33、147.69.148.129、147.69.191.21和147.69.144.16的子网号相同,它们属于同一子网,可以直接相互通信。而主机147.69.127.224和147.69.144.16的子网号不同,它们不属于同一子网,即主机147.69.127.224必须通过路由器才能与主机147.69.144.16进行数据通信。
本试题的另一种解题思路是:求得主机地址147.69.144.16的二进制表示形式为“10010011 01000101 10010000 00010000”后,可知其子网号为“10”,子网地址为147.69.128.0/18,该子网可供分配的主机地址范围为147.69.128.1~147.69.191.254。可见,主机地址147.69.130.33、147.69.148.129、147.69.191.21属于该IP地址范围,而主机147.69.127.224没有落入该IP地址范围。

选择题
阅读理解

阅读理解

     No one has enough, but everyone has all there is. We each have just twenty-four hours in a day. Time

is not our problems , but what we do with the limited time we have is the issue. Many people spend their

days on dozens of activities , but achieve very little because they aren't concentrating on right things. The

Pareto Principle, also known as the 80:20 Rule shows us that typically eighty per cent of unfocused effort

generates only twenty percent of the results. The remaining eighty per cent of the results are achieved

with only twenty percent of the effort . To effectively manage your time, you need to change where you

are spending your time. We all have the same amount of time every day. How you spend your time is

how you spend your life. Here are time management strategies, which may be helpful.

     Learn to say no

     Politely say no should become a habit. Saying no frees up time for the things that are most important.

     Make a "to-do" list

     List the tasks that need to be done in order of their importance. Save other less important things for

when you have time.

Minimize interruption

Plan ahead. Think through projects. Look for ways to "block" interruptions. For example, close your

door, don't answer the phone or work in a different space.

Combine several activities

   Try to do several activities at one time. While going to school,listen to taped notes. This allows up to an

hour or two a day of good study review. While showering,make a mental list of the things. Above all,be

creative,and let it work for you.

1. According to the Pareto Principle, we can know that_________.    

    

A. people can't achieve a lot even though they concentrate on right things

B. people should focus more effort on right and important things and finish them first

C. people are certain to succeed if they spend twenty per cent of their time

D. eighty per cent of effort spent on one matter is useless

2. According to the passage, if you want to do several things on Sunday,you should __________.      

   

A. do them while listening to the music

B. do all of them at one time

C. do the most important one first

D. put some of them off till next Monday

3.The underlined word"block"in the passage means"___________ ".

A. accept      

B. prevent        

C. arrange        

D. defend

4.What would be the best title of the passage?

A. Time Management              

B. The Pareto Principle          

C. How to Make a "To-do" List      

D. Time and Habits