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问题 单项选择题

哪种心脏瓣膜病在直立、运动中易引起晕厥（）。

A.主动脉瓣关闭不全

B.二尖瓣狭窄

C.肺动脉瓣狭窄

D.二尖瓣关闭不全

E.主动脉瓣狭窄

答案

参考答案：E

填空题

一条弦把圆分成2：3两部分，那么这条弦所对的圆周角的度数为___________。
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填空题

Part 2


Questions 9-18


·Read the following passage and answer questions 9-18.
1. From Dr. R. S. Scorer of Britain’s Imperial Collage of the Science comes the latest theory about the lighting flashes. Dr. Scorer believes the cause is haft failing through super cooled clouds. Ice particles bouncing off the falling hail acquire a positive charge and rise to the top of the cloud while the hail carries a negative charge to the bottom of the cloud.
2. According to Dr. Scorer, Benjamin Franklin first proved thunderclouds are charged with electricity. Later investigations showed that the tops of the clouds have a great positive charge and the bottoms have great negative charge.
3. When the charges became great enough to break the insulating properties of the air, lighting flashes carry the electricity within the cloud, or from cloud to cloud, or from cloud to earth. But the question remained: How do the charges develop within the cloud.
4. To seek the cause, Dr. Scorer and his colleagues at the college first duplicated thundercloud current in a liquid tank. They found the mixture takes place only in the tops of the clouds.
5. Next a study of thunderclouds over the North Atlantic showed that the lighting occurs only when the temperature around cloud is below freezing. Particles at the top of the clouds begin to freeze but those in the remainder of the cloud stay unfrozen although below freezing temperature. In the laboratory, S.E. Reynolds whirled a refrigerated rod through ice particles and found that the particles bounced offthe rod acquired a positive charge. This was a missing link. Without hail and super cooled clouds, he concluded, there could be no lighting.

Questions 9-13


·For questions 9-13, choose the best title for each paragraph from below.
·For each numbered paragraph (1-5), mark one letter (A-G) on the Answer Sheet.
·Do not mark any letter twice.
9. Paragraph 1:______
  • A. How the lightning flashes come about.
    10. Paragraph 2:______
  • B. To measure moisture, scientist did the experiment.
    11. Paragraph 3:______
  • C. Two discoveries based on Dr. Scorer’s theory.
    12. Paragraph 4:______
  • D. Significance of Benjamin Franklin’s discovery.
    13. Paragraph 5:______
  • E. Experiments were done to find the cause of lightning.
  • F. Dr. Scorer found the cause of lightning flashes.
  • G. The continuing study of lightning flashes.
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