更多"You can tell the age of a tree by c"的相关试题:
[单项选择]You can tell the age of a tree by counting its ring. But these records of a tree’s life really say a lot more. Scientists are using tree ring to learn what’s been 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 at elements in the rings from a certain years, scientists can tell what elements were in the air that year. Dr. Stevenson is analyzing one element, carbon-d, in ring from both living and dead tree. Some ring go back almost ten thousand year to the end of the Ice Age. When Stevenson followed the carbon-14 levels changed with the intensity of solar burning. You see, the sun has cycles. Sometimes it burns fiercely, and at other times it is relatively calm. During the sun’s violent periods, it throw off charged particles in fast moving streams called "solar winds". The particularly interfere with the formation of carbon14
A. The lifecycle of trees
B. The number of trees
C. The intensity of solar burning
D. The quality of air
[单项选择]
You can tell age of a tree by counting its rings. But these records of a tree’s life really say a lot more. Scientists are using tree rings to learn what’s been 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 at elements in the rings from a certain year, scientists can what elements were in the air that year. Dr. Stevenson is analyzing one element, carbon-14, in rings from both living and dead trees. Some rings go back almost ten thousand years to the end of the Ice Age. When Stevenson followed the carbon-14 track back in time, he found carbon-14 levels changed with the intensity of solar buring. You see, the sun has cycles. Sometimes it burns fiercely, and at other times it’s relatively calm. During the sun’s violent periods, it throws off charged formation of carbon-14 on earth. When there is m
A. examine the chemical elements in the Ice Age
B. look into the pattern of solar wind activity
C. analyze the pattern of solar wind activity
D. find out the origin of carbon-14 on earth
[填空题]Regardless of your age, you can make a number of important changes in your current life style that can help you to become healthier.
[填空题]You can come today. You can also come tomorrow.
You can come ______ today ______ tomorrow.
[单项选择]What can you do if you are not satisfied with its service
A. D．You can do nothing to them in US
[简答题]Each age has its pleasures and its pains, and the happiest person is the one who enjoys what each age gives him without wasting his time in useless regrets. (Passage 1)
