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问题 选择题
已知a=
2
，集合A={x|x≤2}，则下列表示正确的是（　　）
A．a∈AB．a∉AC．{a}∈AD．a⊆A
答案

根据题意，分析选项

对于A、

2
＜2，即有a∈A，A正确；

对于B、

2
＜2，即有a∈A，B错误；

对于C、集合之间符号有误，应为{a}⊆A，C错误；

对于D、元素与集合之间符号有误，应为a∈A，D错误；

故选A．

单项选择题

Who won the World Cup 1994 football game What happened at the United Nations How did the critics like the new play (1) an event takes place, newspapers are on the streets (2) the details. Wherever anything happens in the world, reporters are on the spot to (3) the news.
Newspapers have one basic (4) , to get the news as quickly as possible from its source, from those who make it to those who want to (5) it.
Radio, telegraph, television, and (6) inventions brought competition for newspaper. So did the development of magazines and other means of communication. (7) , this competition merely spurred the newspapers on. They quickly made use of the newer and faster means of communication to improve the (8) and thus the efficiency of their own operations. Today more newspapers are (9) and read than ever before. Competition also led newspapers to branch out into many other fields. Besides keeping readers (10) of the latest news, today’s newspapers (11) and influence readers about politics and other important and serious matters. Newspapers influence readers’ economic choices (12) advertising. Most newspapers depend on advertising for very (13) .
Newspapers are sold at a price that (14) even a small fraction of the cost of production. The main (15) of income for most newspapers is commercial advertising. The (16) in selling advertising depends on a newspaper’s value to advertisers. This (17) in terms of circulation. How many people read the newspaper
Circulation depends (18) on the work of the circulation department and on the services or entertainment (19) in a newspaper’s pages. But for the most part, circulation depends on a newspaper’s value to readers as a source of information (20) the community, city, county, state, nation, and world—and even outer space.

[A] on [B] through[C] with [D] of
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单项选择题

应釆用小风模式进行预测的地曲风速条件是（）。

A.U<0.5m/s

B.0.5m/s≤U≤1.5m/s

C.0.5m/s

D.1.6m/s≤U≤1.9m/s
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