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问题 单项选择题

尘埃能促使天上云形成的根本原因是( )。

A．没有尘埃水汽就无法凝结。

B．尘埃是吸湿性微粒。

C．尘埃可做凝结核。

D．云是由悬浮在空中的水滴和冰晶组成的。

答案

参考答案：B

解析：这与云形成的根本原理相关——水滴和凝结核，尘埃是吸湿性微粒，可使水滴凝结在上面，所以根本原因是它的可吸湿性。

翻译题

阅读下面短文，将文中划线句子译成中文。

　　Some kids in boarding school often like to talk with their roommates. 小题1:They won’t stop talking until someone comes to stop them. This is the reason why many of them are sleepy in class the next day. Lack of (缺乏) sleep is bad for their health. Growth hormones (生长激素) are very important if one is to grow taller. 小题2:The body makes the most hormones between 10 p.m. and 2 a.m. While you are asleep. 小题3:This means that if you don’t get to sleep at the time, you won’t grow taller.
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单项选择题

放置引流的适应证为( )

A．感染和污染创
B．渗液多的创口
C．留有死腔的创口
D．止血不全的创口
E．以上均是
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