问题 单项选择题

高比特率数字用户线(HDSL)是利用现有的什么介质来实现高带宽双向传输

A.电话双绞线

B.电视电缆

C.光缆

D.无线电

答案

参考答案:A

解析:【解析】高比特串数字用户线HDSL是在双纹线环路上实现对称高带宽双向传输的技术。在现有的普通电话双绞铜线 上,上行和下行的传辅速率可达2Mbps。

阅读理解

请品读以下短文,判断句子正(T)误(F)。

     Dogs are friends of man. They work for us. They hunt (狩猎) with us. They play with us. But once,

all over the world, dogs are wild (野生的).

     Dogs go back to the Stoen Age. All dogs had the same ancestor (祖先). It is believed that this

ancestor was much like a wolf (狼). Other animals like the fox, came from this ancestor, too.

     Thousands of years ago, man began to tame (驯服) the wild dogs . When the dogs were tame, they

were trained (训练). The strong dogs became working animals. They were trained to pull heavy loads

(担子). They learned to keep watch over the sheep and other animals. Working dogs had other jobs,

too.

     Some dogs were not strong. But they could help man hunt for game. Other dogs were best as pets.

At first, there were only a few kinds of dogs. Today there are more than 100 kinds.

( )1. The word in the story that means an animal far back in another animal's family is ancestor.

( )2. The story make us believe that Man has helped change animals.                              

( )3. The strong dogs turned into foxes.                                                          

( )4. Dogs are pets from the beginning.                                                          

( )5. Dogs and man have been friends for a long time.                                            

问答题 简答题