以下关于数据报工作方式的描述中，不正确的是______。
A．同一报文的不同分组可以由不同的传输路径通过通信子网
B．在每次数据传输前必须在发送方与接受方之间建立一条逻辑连接
C．同一报文的不同分组到达目的结点时可能出现乱序、丢失现象
D．每个分组在传输过程中都必须带有目的地址与源地址
参考答案：B
解析：[知识点] 数据报方式
[评析] 数据报是报文分组存储转发的一种形式，在数据报方式中，分组传输前不需要预先在源主机与目的主机之间建立“线路连接”，所以选项B是错误的。
数据报方式主要有以下几个特点：
①同一报文的不同分组可以经过不同的传输路径通过通信子网，所以选项A是正确的。
②同一报文的不同分组到达目的结点时可能出现乱序、重复和丢失现象，所以选项C是正确的。
③每个分组在传输过程中都必须带有目的地址和源地址，所以选项D是正确的。
④数据报方式的传输延迟较大，适用于突发性通信，不适用于长报文、会话式通信。
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| Every country has its own culture. Even though each country uses doors, doors may have 1 functions and purposes which lead to 2 differences. When I first to came to America, I noticed that a public building had two different 3 and they had distinct functions. You have to push the door with the word "PUSH" to go out of the building and to pull the door with the word "PULL" to 4 the building. This was new to me, because we use the 5 door in South Korea. For quite a few times I failed to go out of a shopping centre and was embarrassed. The way of using school bus doors was also 6 to me. I used to take the school bus to closes. The school decided that when the driver opened both the front and back doom, 7 who were getting off the bus should get off first, and students who were getting on should get on 8 . in South Korea, we do not need to wait for people to get off. One morning I hurried to the bus, and when the bus doors opened, I 9 tried to get on the school bus through the front door. All the students around looked at me. I was totally 10 , and my face went red. | ||||
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