首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
A、It affects the growth of trees. B、It has been increasing since the Ice Age. C、It is determined by the chemicals in the air. D、
A、It affects the growth of trees. B、It has been increasing since the Ice Age. C、It is determined by the chemicals in the air. D、
admin
2013-11-21
57
问题
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 analyzing 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-14 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.
Questions 20 to 22 are based on the passage you have just heard.
20. What do the scientists want to learn by using tree rings according to the passage?
21. What affects the amount of carbon-14 on earth?
22. What do we learn from the passage about the solar wind activity?
选项
A、It affects the growth of trees.
B、It has been increasing since the Ice Age.
C、It is determined by the chemicals in the air.
D、It follows a certain cycle.
答案
D
解析
细节题。根据短文里科学家推论说太阳风活动也有同碳14一样的周期,可知选D。
转载请注明原文地址:https://kaotiyun.com/show/LVS7777K
0
大学英语四级
相关试题推荐
Choosingwhattodoinlifeisoneofthehardestdecisionsthatapersonhastomake.Somepeoplechoosetooearlyand【B1】_____
What’sthefurthestyouhaveevercycled?Perhapsyoucycletoschoolortowork,ormaybeatmostashortcyclingtripwithfri
A、Hecan’tfindhisnewapartment.B、Hehadabiggerapartmentbefore.C、Hefindsthenewapartmenttoobigforhim.D、He’shavi
A、Sheagreeswiththeman.B、Themanmissedthelaststudysession.C、Shedidn’tunderstandthelastchemistryclass.D、Theman
Agooddealoffascinatingresearchhasbeendoneaboutthereadingpatternsofyoungpeople,anditissurprisingtodiscover
A、Languageelements.B、Culturaldifferences.C、Somethinghappenswhenpeoplefromanotherculturewanttocommunicate.D、Practic
A、Theman’stelephonenumberis647-0547.B、Theman’stelephonenumberis603-0547.C、Themanwasscheduledtomeetthedoctora
A、Totheoffice.B、Toschool.C、Toadepartmentstore.D、Toarestaurant.D男士问:“有时间停下来去吃午饭吗?”女士说:“好的,我饿了。这家快餐店菜式多,价格适中。”因此两人是要去快
A、Confident.B、Hesitant.C、Determined.D、Doubtful.B对话开始,女士问男士:“你认为经理确切的职责是什么?”男士回答说“对这种工作我所知不多”。在女士的一再要求下,男士支支吾吾地说,经理要做许多决策。因此可
Theageatwhichkidsfirstfallvictimtobullying(欺侮)couldinfluencehowstronglytheyareaffected,suggestsanewstudy.And
随机试题
行政程序的主要制度包括()。
关于一张携带病毒的U盘,正确的说法是______。
风险识别的方法包括()
A.心室前负荷加重B.心室后负荷加重C.心室前后负荷均加重D.心肌收缩力减弱E.心肌舒张期顺应性降低急性心肌梗死
根据我国产业结构调整与优化的原则,产业结构调整与优化要与各项配套改革结合起来。这些配套改革包括()。
预收账款是()类账户。
()又称为“华德决策准则”。
Readthetextandthinkofthewordwhichbestfitseachspace.UseoIIlyonewordineachspace.He’salreadyvisitedthepl
假如你是A省B市公安局信访处的一名工作人员。某日一批群众前来上访,为完成工作任务,保障群众利益,领导要求你认真负责此事,面对各种难题,你需要准确解决。当天的第一件工作是处理一件关于某区一名派出所警员无故殴打商贩的网上留言,请问你开展工作的第一步应该是?
下面各组词语中,没有错别字的一组是()
最新回复
(
0
)