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、To learn the chemical elements in the Ice Age for the last ten thousand years. B、To learn the pattern of solar wind activity f
A、To learn the chemical elements in the Ice Age for the last ten thousand years. B、To learn the pattern of solar wind activity f
admin
2015-02-09
40
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、To learn the chemical elements in the Ice Age for the last ten thousand years.
B、To learn the pattern of solar wind activity for the last ten thousand years.
C、To learn the composition of different trees for the last ten thousand years.
D、To learn what’s being happening on the sun’s surface for the last ten thousand years.
答案
D
解析
转载请注明原文地址:https://kaotiyun.com/show/Ldq7777K
0
大学英语四级
相关试题推荐
FreeSchoolMealsA)MillionsofAmericanschoolchildrenarereceivingfreeorlow-costmealsforthefirsttimeastheirparents
A、Surprised.B、Indifferent.C、Respectful.D、Suspicious.C观点态度题。女士为Sullivan先生能够找到500万美元来挽救公司感到高兴,男士说虽然他不知道Sullivan先生究竟是如何做到的,但他真的
Severalyearsago,IlearnedthataphysicianinatownnottoofarfromwhereIwaspracticinghadcommittedsuicide.NeitherI
A、Letherleaveimmediately.B、Getanexperiencedmantohelpher.C、Fireherinaweek.D、Lethergetsomeprofessionaltrainin
Wouldn’titbegreatifyoucouldjustlookupattheskyandreadtheweatherforecastrightaway?Well,youcan.Theforecast
A、Becausethereislargenumberofvocabulary.B、Becausethenon-verballanguagesarenoteasytounderstand.C、Becausethegram
公元220年开始的300年里,中国分成了三个小王国。一个是魏国,位于中国北部,由曹氏家族(theTs’aofamily)统治。还有一个王国叫作蜀汉(ShuHan),位于中国的西南部,由刘备统治。另外一个王国叫作吴国,位于中国的东南部,由孙权(Sun
A、Hewillgotothesupermarketwiththewoman.B、Hefeelsuncomfortablewiththewoman’sstaring.C、Hewillbuysomevegetables
Stuntpeople(替身演员)arenotmoviestars,buttheyarethehiddenheroesofmanymovies.Theywerearoundlongbeforefilms.E
随机试题
用埋弧自动焊单面焊工艺焊接6~20mm厚的钢板的平对接接头可采用()。
A.载药上行B.宁心安神C.健脾助运D.宣肺利气酸枣仁汤中配伍茯苓的作用是
男,32岁。因上前牙不美观要求修复。检查:扭转近90°,且伴有唇侧倾斜。X线片示牙髓正常,牙根形态正常,牙槽骨轻度吸收,牙龈红肿,探易出血。对该患者修复前的准备不包括()
符合下列条件的法典是:()①中国历史上最后一部封建成文法典②中国传统封建法典的集大成者③充分体现了汉唐以来确立的封建法律的基本精神、主要制度④体制为名例律、吏律、户律、礼律、兵律、刑律、工律七部分
根据《保险法》的规定,保险事故发生后,对于保险合同各方的责任,下列表述正确的是()。
关于柔性管道质量检验方法、标准及超标处理的说法,正确的是()。
债务重构通常发生的原因有()。
下列属于浙江省的民间音乐的有()。
下列关于数据库设计的叙述中,正确的是
1.打开工作簿文件EX10.XLS(内容如下),将工作表sheetl的A1:D1单元格合并为一个单元格,内容居中;计算“金额”列的内容(金额=数量×单价),将工作表命名为“购买办公用品情况表”。2.打开工作簿文件EX10.XLS,对工作表“购买办公用
最新回复
(
0
)