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问题 选择题

图四条曲线代表的是美、德、英、中四个国家制造业产值在世界上所占比重，结合所学知识推断，其中代表美国的曲线应该是（  ）

A．①

B．②

C．③

D．④

答案

答案：C

题目分析：曲线一应该是英国，在第一次工业革命时期领先世界，在第二次工业革命后开始落后于美德两国。美国在第二次工业革命后开始领先世界，到1898年时工业总产值居世界之首，所以由图示中的事时间数据与曲线的高度可知④是美国。

单项选择题

The usual way to ensure reliable delivery is to provide the (16) with some feedback about what is happening at the other end of the line. Typically, the protocol calls for the receiver to send back special (17) frame bearing positive or negative (18) about the incoming frames. If the sender receives a positive acknowledgement about a frame, it knows the frame has arrived safely.On the other hand, a negative acknowledgement means that something has gone wrong, and the frame must be transmitted again. An additional complication comes from the possibility that hardware troubles may cause a frame to (19) completely. In this case, the receiver will not react at all, since it has no any reason to react. It should be clear that a protocol in which the sender transmits a frame and then waits for an acknowledgement, positive or negative, will hang forever if a frame is ever lost due to, for example, (20) hardware.

（20）是（）

A.acting

B.working

C.malfunctioning

D.functioning
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问答题 简答题

监测资料分析的常规方法中，什么是比较法？试述比较法的基本办法。
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