在民航使用的无线电系统中,利用电离层通信的是( )。

在民航使用的无线电系统中,利用电离层通信的是( )。A.甚高频通信系统 B.微波通信系统 C.卫星通信系统

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(  ) What is the author's attitude towards bad hab

(  ) What is the author's attitude towards bad habits?A.Negative. B.Ob

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(  ) A lot of friends advise him not to drink more

(  ) A lot of friends advise him not to drink more wine_______is good

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根据以下材料,回答题On November 19,1863, Abraham Lincoln went to Getty

根据以下材料,回答题On November 19,1863, Abraham Lincoln went to Gettysburg in Pennsylvan

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(  ) According to the passage, what is the most ef

(  ) According to the passage, what is the most effective exercise tim

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