为了实现数据终端设备之间的通信，在通信网络中必须设置交换中心，以便为需要通信的数据终端建立通信链路，通信结束后再拆除链路。目前在视频会议中使用的交换技术主要是：
A．报文交换
B．电路交换
C．分组交换
D．信元交换
参考答案：B
解析：【解析】交换方式可分为电路交换、报文交换和报文组交换(又称包交换)三大类。电路交换是通过电路转换，在交换机输入与输出之间建立用户所需的通信线路。目前在视频会议中使用的是电路交换。
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 When you step into a new environment, you must have a strong wish to fit in. Fitting in means making more friends, __1__ more influence on others and getting more chances to live a happier life. Here is some__2__ that can help you. Be confident. Confidence attracts most people. Everyone is special and there is only one person like you in this world. Spend__3__ thinking about your strong points. If so, you will be able to build up confidence step by step. You won't have much difficulty fitting in. Be kind to everyone. Kindness is the bridge to your own happiness.__4__ people notice your kindness, they will return it one day. Always give more than you receive, and think more of others than of __5__. A person who cares for others is popular everywhere. Be active in group activities. Various activities like playing football__6__ help you to be known to others. You may add more friends to your circle. At the same time, you'll be amazed to see how much they like you. __7__ wasting time being alone, go out to dance and sing together with others to develop friendship. Be optimistic. Optimism makes both you and others feel pleased. It makes a good first impression. A pleasant smile costs the __8__ and does the most. Humor catches others' attention as well. People will like you for making them live __9__. If you follow what is mentioned above, you__10__ by people around you. As a result, you will fit in very well and enjoy your new life. | |||
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