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问题 单项选择题

在OSPF网络中，路由器定时发出Hello分组与特定的邻居进行联系。在默认情况下，如果______没有收到这种分组，就认为对方不存在了。

A．20秒

B．30秒

C．40秒

D．50秒

答案

参考答案：C

完形填空

Dear Sir,

I’m glad to recommend to you my student Li Ming.

Li Ming was born ____小题1:__ July 15,1974 in Xiamen. He studied in Datong Primary School from 1980. When he was in the m___小题2:__school, he did ___小题3:___ in maths, physics and chemistry and wasfond of art. After ___小题4:___(毕业) from No.6 High School, he entered Beijing University to s__小题5:____ physics. After four years of hard work there, he went to the United States for f__小题6:____ study. Because of his excellent work, he got a __小题7:_____(博士) degree in physics this year. He is now in good health and would __小题8:_____ to make contributions（贡献） to our country.

I should be most ___小题9:___(感激) if you would favorably consider my recommendation.

Looking forward to ___小题10:___ from you.
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填空题

写出下列方程式

（1）氨气与氧气的反应（氨的催化氧化）______

（2）铜与浓硝酸反应______．
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