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问题 单项选择题

某单回路500kV架空送电线路，采用4分裂LGJ-400/35导线，导线的基本参数如表。

该线路的主要气象条件为：最高温度40℃，最低温度-20℃，年平均气温15℃，最大风速30m/s（同时气温-5℃），最大覆冰厚度10mm（同时气温-5℃，同时风速10m/s）。且重力加速度取10。

若代表档距为500m，年平均气温条件下的应力为50N/mm2，最高气温时的应力最接近下列哪项值？（）

A.58.5N/mm2

B.47.4N/mm2

C.50.1N/mm2

D.51.4N/mm2

答案

参考答案：B

选择题

辛亥革命实现了20世纪中国第一次历史性巨变，主要是因为这次革命 [ ]

A．孙中山众望所归地被推举为临时大总统

B．彻底结束了帝国主义在中国的殖民统治

C．宣告了中国2000余年帝制的终结

D．在中国第一次真正实现了人民当家作主

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单项选择题

The following two questions are based on the following passage:

A study by a group of dentists has concluded that regular use of a certain brand of mouthwash is as effective as flossing in preventing gum disease. The mouthwash company has released a television ad suggesting that people who do not like flossing can now rely solely on mouthwash and brushing to maintain good dental health. A leading manufacturer of dental floss brought a lawsuit against the mouthwash company demanding that the advertisement be discontinued on the grounds that it is misleading.

Which of the following, if true, provides the pest support for the dental floss company’s claim that the advertisement is misleading ？（）

A. The dental floss manufacturer is concerned that it will lose market share in the dental health market because the advertisement encourages people to switch from dental floss to mouthwash.

B. The dental floss company claims in its own advertisements that brushing and flossing after every meal is the most effective way to maintain good dental health.

C. Although mouthwash is an effective deterrent to gum disease, it is less effective than dental floss at removing plaque and preventing cavities between teeth.

D. Per usage, mouthwash is three times more expensive than dental floss, if the recommended amounts of both products are used.

E. The dentists who conducted the study on the effectiveness of mouthwash in preventing gum disease obtained their funding for the study from a company that manufactures mouthwash.
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