在OSI参考模型的各层中，向用户提供可靠的端到端(End-to-End)服务，透明地传送报文的是( )。
A．应用层
B．数据链路层
C．传输层
D．网络层
参考答案：C
解析： 在OSI参考模型的各层中，传输层的主要任务是向用户提供可靠的端到端(End to End)服务，透明地传送报文。传输层向高层屏蔽了下层数据通信的细节，因而是计算机通信体系结构中最关键的一层。
| 阅读下面短文，把方框中的句子还原到文中，然后完成第5小题。 | |||
 Do you know Weibo? Do you write a Weibo? If you don't, you are "out"! Weibo means mieroblog. People may spend much time writing a blog, but it takes a little time to write a mieroblog. Why? 1 Microblog started in the USA. It came to China in 2009 and it has developed very fast. In 2011, the number of Chinese micro-bloggers grew to 300 million. 2 For many microblog users, it is a great way of learning the freshest news, talking with friends and sharing different kinds of information, including news, daily life, pictures, music and so on. Many stars and famous people also write microblogs and share good things with their fans. It is easy and fast to send a message on a microblog. 3 For example, when the big earthquake and tsunami (海啸) hit Japan in March, 2011, messages like " Salt can protect people from radiation" were hot on microblogs. 4 Later people realized it was just a rumor (谣言). In a word, microhlog plays a new role in the life of Chinese people. | |||
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| 5. Which of the following is TRUE? | |||
| A. Writing a microblog needs much time. B. Microblog appeared in China only one year ago but it has developed rapidly. C. As a popular thing, microblog has its advantages and disadvantages. D. More and more Chinese show great interest in microblog because it started in the USA. | |||