问题
单项选择题
根据OSI（开放系统互连）参考模型，UDP协议是属于下列哪个层次的协议？（）
A.传输层
B.网络层
C.链路接入访问控制子层
D.介质访问控制子层
答案
参考答案：A
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根据OSI（开放系统互连）参考模型，UDP协议是属于下列哪个层次的协议？（）
A.传输层
B.网络层
C.链路接入访问控制子层
D.介质访问控制子层
参考答案：A
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| In each country, there are some places of interest, like Big Ben in Britain, the Great Wall in China and so on. So you must 1 _ the Leaning Tower of Pisa(比萨斜塔). But do you know why it leans (倾斜)? It leans 2 _ a mistake. In 1173, people of 3 _ wanted to build a bell tower. They wanted the tower to be 4__bell tower in the whole country. Before people finished 5 _ the third floor of it, the tower began to lean. People tried to make the building 6 _ again. However, as they added(增加) more floors, the tower only got 7__. It 8 _ almost 180 years to finish the tower. Today, the Leaning Tower has eight floors. It’s 54.5 meters tall, and it leans about 5 meters to one 9 _. If someone cannot think out a good way 10 _ the tower, like all the other old buildings, it’ll fall apart(倒塌) in the future. | ||||
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