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问题 单项选择题

在一项评价流感减毒活疫苗效果的研究中，接种组流感的发病率为2.5%，对照组流感的发病率为25%，该疫苗的保护率为

A．10%
B．25%
C．50%
D．75%
E．90%

答案

参考答案：E

解析：保护率=(对照组的发病率-实验组的发病率)/对照组的发病率×100%。

完形填空

阅读下面短文,将所给的五个句子填入空白处,是短文意思完整正确.(计5分)

Now satellites are helping to forecast(预报) the weather . 小题1:______The satellites take pictures of the atmosphere(大气),because this is where the weather forms(形成). 小题2:______So the scientists there can see the weather of any part of the world and tell how the weather will change.

Today, nearly five hundred weather stations in sixty countries can receive satellite pictures. When they receive the new pictures ,they compare(比较) them with the earlier ones . 小题3:_______This may mean that the weather forecast, 小题4:_______

So the weather satellites are of a great help to the scientists at the station. 小题5:________Now they can make good forecasts for 3 or 5 days .Soon perhaps, be  able to forecast the weather for a week or more ahead(提前).

A．In the past they could forecast the weather for about 24 or 48 hours earlier.

B．They send these pictures to the weather station .

C．they can tell people about it .

D．They are in space , and they can reach any part of the world .E. Perhaps they may find that the clouds have changed during the last few hours.
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填空题

降低冲财力的方法之（）。
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