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问题 单项选择题

相互接触的物体之间，有相对运动或有相对运动的趋势时，则接触面上就有摩擦力，摩擦力的方向与物体的运动方向或相对运动趋势（）

A．相同

B．垂直

C．相反

D．无关

答案

参考答案：C

翻译题

阅读下面短文，将短文中画线部分的句子翻译成中文

How Much Water Is Needed a Day?

Many people think they should drink eight glasses of water a day．Why? Because that is what they have been told all their life．But a new report on science gives some different suggestions：people should drink according to their bodies．112．They should drink as much water as they would like to drink．

The report says most people meet their daily needs for water by letting thirst be their guide．It also gives people some good suggestions：women should get about 2.7 liters（升）of water every day，while men should get about 3.7 liters．

There is an important difference．113．The report doesn’t tell people how many glasses of water to drink．Instead，the experts say it may not be possible to know how many glasses people really need．This is because the daily want of water can include the water in foods．
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单项选择题

以下关于操作型数据和分析型数据的描述中，错误的是

A．操作型数据是详细的，而分析型数据是综合的

B．操作型数据在存取瞬间是准确的，而分析型数据则代表过去的数据

C．操作型数据很少更新，而分析型数据需要不断更新

D．操作型数据的操作需求事先可知道，而分析型数据操作的需求事先不知道
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