问题 单项选择题

目前主要的运营网络有电信网、有线电视网和计算机网。其中______采用电路分组和分组交换实现各用户之间的通信。

A.电信网

B.有线电视网

C.计算机网

D.三者都是

答案

参考答案:A

解析:[知识点] 网络技术展望[评析] 目前主要的运营网络有电信网、有线电视网和计算机网,其中电信网采用电路分组和分组交换实现各用户之间的通信,从交换局到用户之间为点到点连接,它为通信双方建立了一条端到端的通信链路。

阅读理解

阅读理解。

     Animals seem to have the sense to eat when they are hungry and they do not eat more than their bodies

need. It has been shown that rats will, when given a choice over a period of time, prefer water with

vitamins to water without vitamins even there is no difference in taste or smell between the two water

bottles. When a fragrant flavor (香味) was added to the vitamin-enriched water, the rats did seem to

develop a taste for it and kept drinking it, even after the vitamins were switched to the clear water. In time,

however, they broke the habit and went back to where the necessary vitamins were.

     In a classic experiment, babies of 6 to 12 months old were placed in a cafeteria feeding arrangement,

with a wide selection of baby food before them. They were given whatever they pointed to or appeared

interested in. We are told that at first they showed some unusual eating patterns (方式), but over a period

of time they managed to select well-balanced diet.

     So, in selecting food, rats and babies do seem to know and act on what's best for them. Apparently,

there is a kind of "body wisdom", which humans soon lose. Most of us do not eat as wisely as we could. Many of our food preferences are culturally determined and influenced by long established habits. Some

people eat foxes, dogs and blackbirds, while we eat cows and pigs. So what people eat and how much

they eat seems to be greatly influenced by what is going on around them.

1. As far as their eating habits are concerned, babies and rats are similar in that both _____.

A. have the natural abilities to choose a balanced diet

B. develop a taste for the same kinds of flavors

C. have the same eating patterns

D. prefer flavored food and drink

2. In the experiment on rats, a fragrant flavor was added to the water to _____.

A. prove that vitamins are tasteless

B. find out rats preference in flavor

C. encourage rats to drink vitamin-enriched water

D. test whether rats know which drink is good for them

3. According to the passage, adults eating habits differ from those of babies because _____.

A. adults have more choices of food than babies in eating patterns

B. adults usually cannot resist the temptation of various delicious food

C. adults' eating habits are closely related to the social and culture customs

D. adults know better than babies what kinds of food are good for their health

单项选择题