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 find out the origin of carbon- 14 on Earth. B、To analyze the composition of different trees. C、To look into the pattern of
A、To find out the origin of carbon- 14 on Earth. B、To analyze the composition of different trees. C、To look into the pattern of
admin
2012-09-19
37
问题
You can tell the age of a tree by counting its tings. But these records of a tree’s life really say a lot more. Scientists are using tree tings 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 the elements in the rings from a 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 bums fiercely. At other times it’s relatively calm. During the sun’s violent periods, it throws off charged particles in fast moving streams, called solar winds. The particles interfere with the formation of carbon—14 on earth. When there is more solar wind activity, less carbon—14 is produced. Ten thousand years of tree rings show the carbon—14 level rises and falls about every four hundred and twenty years. The scientists concluded that solar wind activity must follow the same cycle.
选项
A、To find out the origin of carbon- 14 on Earth.
B、To analyze the composition of different trees.
C、To look into the pattern of solar wind activity.
D、To examine the chemical elements in the Ice Age.
答案
C
解析
转载请注明原文地址:https://jikaoti.com/ti/2pcFFFFM
0
大学英语四级
相关试题推荐
A、Mrs.Fisherwantstogoabroad.B、Mrs.Fisherisinhospital.C、Mrs.Fisherhasnofamily.D、TherearethreepeopleinMrs.Fi
Itisdifficulttobelievethat,onlyeightyyearsago,theideaofthedomesticelectriclightwasheldincontemptbyallthe
Publicimage【C1】______tohowacompanyisviewedbyitscustomers,suppliers,andstockholders,bythefinancialcommunity,byt
SleepSleepisoneofthosefunnythingsaboutbeingahumanbeing--youjusthave’todoit.Haveyoueverwonderedwhy?A
Whatdowemeanbybeing’talented’or’gifted’?Themostobviouswayistolookattheworksomeonedoesandiftheyarecapabl
Oneofthemostimportantfeaturesthatdistinguishreadingfromlisteningisthenatureoftheaudience.【67】thewriteroftendo
ThelargeAmericanenergyservicecompany,Enron,failedafewyearsago.IthadbeentheseventhlargestcompanyintheUnited
Atsometimeinyourlifeyoumayhaveastrongdesiretodosomethingstrangeorterrible.【C1】______,chancesarethatyoudon
A、BusyLifeforPetsB、PetsJointheWorkforceC、YourFavoriteOfficePetsD、PetsHelpAttractCustomersB由选项实词首字母均大写可知本题考查短文标题。
Havingsettledinthatremotearea,theyoungmanquickly______(适应了那里恶劣的天气)
随机试题
以下集成块型号中属于MCS-51系列单片机型号的是()
A.机体连续多次用药后,其反应性降低,需加大剂量才能维持原有疗效的现象B.反复使用具有依赖性特征的药物,产生一种适应状态,中断用药后产生的一系列强烈的症状或损害C.病原微生物对抗菌药的敏感性降低甚至消失的现象D.连续用药后,可使机体对药物产生生理/心
以下法律冲突的解决方法中,属于间接调整方法的有:
根据有关规定,建设工程项目材料采购投标文件应包括()等内容。
创设一定情景让受训者扮演“教师”和“学生”等不同角色,用类似演戏的方式以提高其教学技能水平的方法是()。
社会可以制约教育的发展,而教育无法制约社会的发展。()
整风运动,一般又称作延安整风,是中国共产党自1942年2月开始在陕甘宁边区延安根据地所发动的一场政治和文化运动,持续了约3年时间。所谓的整风是指“整顿三风”,包括“反对主观主义以整顿学风,反对宗派主义以整顿党风,反对党八股以整顿文风”。延安整风运动的历史意
设函数f(x)满足等式且f(0)=2,则f(π)等于()
AftersomanyyearsofstudyingEnglish,youmaystillgetconfusedlikeyoufirstcomeherejustbecauseoftheslangthestude
ObesityAttheotherendofthemalnutritionscale,/obesityisoneoftoday’smostvisible,yetmostneglected,publichea
最新回复
(
0
)