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问题 单项选择题

一个大气压下20℃的空气平行流过平板，速度为3.5m/s。利用布拉修斯精确解，则x=1m处的边界层厚度为( )。

A．δ=1.025cm
B．δ=1.035cm
C．δ=1.045cm
D．δ=1.055cm

答案

参考答案：B

填空题
用所给词语的适当形式填空，使短文正确、通顺、连贯。（每词限用一次）
hear, took, grew, healthy, slowly, himself, something, operation, to help, sad

     James was a boy. He was different from other children. He did everything 1             . His parents did
not know what was wrong. So they went to the doctor's. The doctor found that the boy could not see 2             .And he said that he could do nothing 3              him. James' parents were even 4             .
     James 5              big as time went on. He was 6              and happy. But he could not look after
7             . One day his parents 8              that there was a good doctor in a town. They 9              the
boy to see him. The doctor did a small 10              and James could see clearly. How happy everyone
feels!

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选择题

下列哪个国家不可能出现“白色圣诞”[ ]

A．加拿大

B．英国

C．澳大利亚

D．俄罗斯
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