导语:以下英语网为大家整理了全面的职称英语考试历年真题及答案解析,《职称英语考试试题汇总:历年真题及答案解析》供大家参考学习。更多职称英语考试试题敬请关注英语网!
第2部分:阅读判断(第16~22题,每题1分,共7分)
下面的短文后列出了7个句子,请根据短文的内容对每个句子做出判断:如果该句提供的是正确信息,请选择A;如果该句提供的是错误信息,请选择B;如果该句的信息文中没有提及,请选择C.
Radiocarbon Dating
Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射性碳), or carbon-14, dating. One key to understanding how and by something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at he University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons(中子) and six neutrons (质子) in its nucleus. Carbon-14, or C-14, is a radioactive, unstable form of carbon that has two extra neutrons (原子核)。 It returns to a more stable form of carbon through a process called decay (衰减)。 This process involves the loss of he extra neutrons and energy from the nucleus.
In Libbys radiocarbon dating technique, the weak radioactive emissions (放射) from his decay process are counted by instruments such as a radiation detector and counter. He decay rate is used to determine the proportion of C-14 atoms in the sample being dated.
Carbon-14 is produced in the Earths atmosphere when nitrogen (氮)-14, or N-14,
interacts with cosmic rays (宇宙射线)。 Scientists believe since the Earth was formed, the mount of nitrogen in the atmosphere has remained constant. Consequently, C-14 formation is thought to occur at a constant rate. Now the ratio of C-14 to other carbon toms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years.
All life on Earth is made of organic molecules (分子) that contain carbon atoms coming from the atmosphere. So all living things have about the same ratio of C-14
atoms to other carbon atoms in their tissues (组织)。 Once an organism (有机体) dies it tops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 in the material decreases, and the ratio of C-14 to other carbon toms goes down. In terms of radiocarbon dating, the fewer C-14 atoms in a sample, the older that sample is.
16 Nowadays many scientists depend on radiocarbon for dating age-old objects
A Right B Wrong C Not mentioned
17 The radiocarbon dating technique is only about 40 years old
A Right B Wrong C Not mentioned
18 An atom of ordinary carbon has six protons and eight neutrons
A Right B Wrong C Not mentioned
19 Radar is used to determine the characteristics of radiocarbon.
A Right B Wrong C Not mentioned
20 Radiocarbon is reliable in dating an object back to at least 50,000 years.
A Right B Wrong C Not mentioned
21 When an organism dies, the C-14 in it begins to decay.
A Right B Wrong C Not mentioned
22 The half-life of C-14 is about 25,000 years.
A Right B Wrong C Not mentioned
国内英语资讯:China provides emergency food aid to Afghanistan before winter
常用漱口水或增加患心脏病风险
体坛英语资讯:Kenyas Jepkosgei to return to Valencia for World Half marathon
国际英语资讯:Firestorm over questionable 300 mln USD contract to restore Puerto Rico power
体坛英语资讯:Colombia striker Borja seeking Atletico Nacional return
报告指出 分享经济吸纳我国5%的劳动力
体坛英语资讯:Ding scores 42 points as Shandong edge Shanxi in CBA opener
体坛英语资讯:Messi and Ter Stegen help Barca make it 9 from 10
国内英语资讯:Mainland to continue promoting peaceful development of cross-Strait relations
10款最适合万圣节的自制小甜点![1]
国际英语资讯:Iraqi-Kurdish talks make progress despite pending points
最新报告显示 我国休闲市场商机巨大
国际英语资讯:Laos sets to promote tourism, preserve unique, fine traditional culture
中国成为亚洲最大的留学目的国
美文赏析:请让自己值得拥有爱情
全球首个机器人公民沙特诞生
体坛英语资讯:Rock n Roll Marathon makes impressive debut in China
国内英语资讯:Chinese technology company provides 680,000 USD worth CSR assistance to Myanmar in 2016-17
《孤独星球》:2018年去这10个城市旅游吧(组图)
国内英语资讯:Chinese astronaut Yang Liwei among first UNESCO Space Science Medal winners
大三学生通过零食盒子创业 室友足不出户可扫码消费
国际英语资讯:Visa waiver helps boost tourism in LatAm trade bloc
全球首个机器人公民沙特诞生
国际英语资讯:Turkey marks Republic Day at 94th anniversary of its establishment
国际英语资讯:Interview: APEC summit to bring regional cooperation closer to people, businesses: Vietnames
国际英语资讯:UN mission urges probing into killing of dozens in Libya
去中国吧,你会爱上她!美版“知乎”用户为中国点赞!
国际英语资讯:Confidence in U.S. political system lowest in decades: poll
国内英语资讯:China, Bangladesh sign framework agreement on oil pipeline project
体坛英语资讯:Zheng and Chen fail to defend, Chinese team miss out top podium at BWF French Open