问题 单项选择题

一装置采用8251A进行同步通信,当选定通信速率为9 600波特时,施加于8251A芯片的TxC及RxC引脚上的时钟信号频率为()。

A.4800Hz

B.2400Hz

C.19200Hz

D.9600Hz

答案

参考答案:D

解析:TxC:发送器时钟,用于控制825lA发送字符的波特率。TxC在同步方式时,应与发送、接收波特率相等:在异步方式时,可以是波特率的1倍、16倍或 64倍。

单项选择题 A1/A2型题
阅读理解

Ⅲ 阅读(共两节。满分40分)

第一节阅读理解(共15小题;每小题2分,满分30分)

阅读下列短文,从每题所给的A、B、C和D项中,选出最佳选项,并在答题卡上将该项涂黑。

A

Good health is the most valuable thing a person can have, but one cannot take good health for granted. It is important to remember that the body needs proper care in order to be healthy. There are three things that a person can do to help stay in good shape: eat right food, get enough sleep, and exercise regularly.

Proper nutrition (营养) is important for good health. Your body cannot work well unless it receives the proper kind of “fuel”. Don't eat too much food with lots of sugar and fat. Eat plenty of foods high in protein (蛋白质) , like meat, fish, eggs and nuts. Vegetables and fruits are very important because they provide necessary vitamins (维他命) and minerals. However, don't overeat. It is not helpful to be overweight.

Getting the proper amount of sleep is also important. If you don't get enough sleep, you feel tired and easily get angry. You have no energy. Over a long period of time a little amount of sleep may even result in a change of personality. Be sure to allow yourself from seven to nine hours of sleep each night. If you do, your body will feel strong and refreshed, and your mind will be sharp.

Finally, get plenty of exercise. Exercise firms the body, strengthens the muscles, and prevents you from gaining weight. It also improves your heart and lungs. If you follow a regular exercise program, you will probably increase your life-span (寿命).Any kind of exercise is good. Most sports are excellent for keeping the body in good shapes: basketball, swimming, bicycling, running and so on are good examples. Sports are not only good for your body, but they are enjoyable and interesting, too.

If everybody were to eat the right foods, get plenty of sleep and exercise regularly, the world would be a happier and healthier place. We would all live to be much older and wiser.

41. According to the passage,_________.

A .we should always keep fit

B. if we were healthy, we could spend our days in doing things with less sleep

C. one can eat a lot to stay in good shape

D. one needn't take any exercise if he is healthy

42. In order to keep good health, ___________ .

A. we should eat a lot of sweets      

B. one needs a large amount of fat

C. people should eat according to the foods nutrition

D. we must try to sleep now and then

43. Eating more and sleeping less________.

A. can keep healthy                 B. is no good for you

C. gets you more energy           D. will keep your personality

44.The writer explains ________in this passage.

A. how to eat                         B. the importance of doing exercise

C. how to keep healthy             D. what to eat

45.The title of the article should be___________ .

A. Eating and Exercising           B. How Vitamins Work in Man's Body

C. Staying Healthy                   D. Sleeping Well