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
2017-02-24
20
问题
You can tell the age of a tree by counting its rings. But these records of 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 a tree grows, it adds a layer to its trunk taking up chemical elements from the air. By looking up the elements in the rings from the given year, scientists can tell 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 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 is 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 16 to 18 are based on the passage you have just heard.
16. What is the purpose of the scientists in studying tree rings?
17. What affects the amount of carbon-14 on earth?
18. 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
事实细节题。根据短文最后一句The scientists concluded that the solar wind activity must follow the same cycle,可知太阳风的活动遵循着一个相同的周期。所以选D。
转载请注明原文地址:https://kaotiyun.com/show/8ki7777K
0
大学英语四级
相关试题推荐
Companiesaroundtheglobehaveworktodotoimproveworkersatisfaction,becausethreeintenemployeessaytheirworkplaceis
Companiesaroundtheglobehaveworktodotoimproveworkersatisfaction,becausethreeintenemployeessaytheirworkplaceis
A、Theyarearguing.B、Theyarebargaining.C、Theyarecomplaining.D、Theyarenegotiating.C男士说自己工作多、电话多,女士说就连周末她也有很多电话。可见他们在抱怨工
Memoryisourmostimportantpossession.Withoutmemory,youwouldn’tknowwhoyouare.Youcouldn’tthinkaboutthepastorpla
Memoryisourmostimportantpossession.Withoutmemory,youwouldn’tknowwhoyouare.Youcouldn’tthinkaboutthepastorpla
ForAmericans,timeismoney.Theysay,"Youonlygetsomuchtimeinthislife;you’dbetteruseitwisely."Thefuturewillno
A、Theyarequitedifferentinpaintingskills.B、Neitherofthemisgoodathouse-painting.C、Theyareequallygoodathouse-pai
A、Intheclassroom.B、Atthepostoffice.C、Inthebank.D、Inapark.B女士说:“我想以第一类邮件的方式寄这个包裹,另外我还想买几张邮票。”男士回答:“你的邮寄物品需要买保险吗?”可见对
A、Naturaldisasters.B、Largechemicalfactories.C、Exhaustfromvehicles.D、Largeamountsofhouseholdgarbage.B男士说汽车尾气给环境造成很大的
A、Itmeanstheyearyoutakeoffandyou’llcontinueschoolwithenoughmoney.B、Itmeanstheyearyouhaveoffbetweenhighsch
随机试题
调查研究有文献查阅和社会调查两种途径。
根据德国基本法,下列选项中属于各州专有立法范围的是()
能力的个别差异主要表现在哪些方面?如何根据能力的个别差异因材施教?
在计算机内部,程序是由指令组成的。大多数情况下,指令由______和操作数地址两部分组成。
颌面外伤清创时只能清除的组织是
0.55g0.20g
真空管道进行气压试验时,其试验压力应为()。
企业利用自有仓库储存存货的变动成本有()。
我们对“市场经济体制”的认识,30年来先后经历了四个阶段:“计划经济为主,市场调节为辅”阶段、“有计划的商品经济”阶段、“计划经济与市场调节相结合”阶段、“建立社会主义市场经济体制”阶段。这一认识过程表明()。①每一时期的人们对客观事物的
派生需求也称为引致需求,它是指对生产要素的需求,意味着它是由对该要素参与生产的产品的需求派生出来的。根据上述定义,以下属于派生需求的是()。
最新回复
(
0
)