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You can tell the age of a tree by counting its rings, but these records of trees' life really say a lot more. Scientists are using tree rings to learn what's being happening on the sun's surface for the last ten thousand years. Each ring represents a year of growth. As the tree grows, it adds a layer to its trunk taking up chemical elements from the air. By looking up the elements in the rings for a given year, scientists can tell what elements were in the air that year. Doctors Stevenson is analysing one element——carbon-14 in ring from both living and dead trees. Some of the rings go back almost ten thousand years to the end of the Ice Age. When Stevenson followed the carbon-14 trail back in time, he found carbon-4 levels change with the intensity of solar burning. You see, the sun has cycles. Sometimes it burns fiercely and other times it's relatively calm. During the sun's violent periods, it throws off charged particles in fast moving strings called solar winds. The particles interfere with the formation of carbon-14 on earth. When there's more solar wind activity- less carbon-14 is produced. Ten thousand years of tree rings show that the carbon-14 level rises and falls about every 420 years. The scientists concluded that the solar wind activity must follow the same cycle.
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【判断题】希腊神话中的哈迪斯(Hades)掌管战争。
A.
正确
B.
错误
【单选题】。建国君民,教学为先”这句话摘自《礼记》,是中国古代教育强国思想的最早体现。中国古代政治家管仲曾说:“夫争天下者,必先争人。”苟子曾阐述了百年树人的思想:“一年之计,莫如树谷;十年之计,莫如树木;终身之计,莫如树人。”唐朝战略思想家李筌在《太白阴经》中指出:“国愚则智可以强国,国智则力可以强人。用智者,可以强于内而富于外;用力者,可以富于内而强于外。”以智强国,充分体现了我国古代思想家对教育的重视...
A.
中国古代思想家对教育十分重视
B.
中国教育观念的变化
C.
中国古代教育家的著名观点
D.
中国古代的教育思想强国
【单选题】吞噬性溶酶体类型
A.
自噬性溶酶体
B.
异噬性溶酶体
C.
残余小体
D.
以上都对
E.
以上都不对
【多选题】What does the Western societies not value?
A.
Individualism, independent thinking, and initiative.
B.
Discipline and self-control.
C.
Cooperation.
D.
Vicious competition.
【判断题】手性化合物不一定含有手性碳原子,有手性碳原子的化合物却一定具有手性。
A.
正确
B.
错误
【单选题】The Sun Also Rises and A Farewell to Arms were written by .
A.
F. Scott Fitzgerald
B.
Jack London
C.
Henry James
D.
Ernest Hemingway
【简答题】失速的直接原因
【单选题】The _____ of A Farewell to Arms is Hemingway.
A.
assistant
B.
aunt
C.
author
D.
artist
【简答题】含有手性碳原子的化合物不一定有 性。
【单选题】_______ serves as the background for the novel A Farewell to Arms.
A.
Spanish Civil War
B.
World War I
C.
World War II
D.
Mexican-American War
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