首页
财务会计
医药卫生
金融经济
考公考编
外语考试
学历提升
职称考试
建筑工程
IT考试
其他
登录
职称考试
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...
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...
admin
2020-12-24
74
问题
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 why something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons(质子)and six neutrons(中子)in its mKJteus(原子核).Carbon-14, or C-14, is a radioactive.
unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay ( 衰减). This process involves the loss of the extra neutrons and energy from the nucleus.
In Libby’s radiocarbon dating technique, the weak radioactive emissions (放射) from this decay process are counted by instruments such as a radiation detects and counter. The decay rate is used to determine the proportion of C-14 atoms in the sample being dated.
Carbon-14 is produced in the Earth’s atmosphere when nitrogen (氮)-14,or N-14, interacts with cosmic rays (宇宙射线). Scientists believe since the Earth was formed,the amount of nitrogen in the atmosphere has remained constant. Consequently, C-14 formation is thought to occur at a constant rate. Now ratio of C-14 to other carbon atoms 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 atmosphem. 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 stops 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 atoms goes down. In terms of radiocarbon dating, the fewer C-14 atoms in a sample, the older that sample is.
An atom of ordinary carbon has six protons and eight neutrons.
选项
A Right
B Wrong
C Not mentioned
答案
B
解析
转载请注明原文地址:https://ti.zuoweng.com/ti/tElQKKKQ
相关试题推荐
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有15处空白,请根据短文内容为每处空白确定1个最佳选项。 YoungAdultsWhoExerciseGetHigher...
下面的短文有5处空白,短文后有6个句子,其中5个取自短文,请根据短文内容将其分别放回原有位置,以恢复文章原貌。 Mt.DesertIs...
下面的短文有5处空白,短文后有6个句子,其中5个取自短文,请根据短文内容将其分别放回原有位置,以恢复文章原貌。 Mt.DesertIs...
下面的短文有5处空白,短文后有6个句子,其中5个取自短文,请根据短文内容将其分别放回原有位置,以恢复文章原貌。 Mt.DesertIs...
随机试题
在资金等效值计算过程中,终值是指资金运动结束时发生的实际金额。( )
填入下列横线处最恰当的一项是: 美国有不少著名的礼貌程序,多少年来______
增资前甲公司注册资本1000万元,甲公司前一年度经审计的营业收入12亿元,净利润
《涉外民事或商事案件司法文书送达问题若干规定》对涉外民事或商事案件司法文书送达中
C将直线写成参数方程后求解
实际工资的计算公式是()。
如果飞机进近航道稍低于正确航道,驾驶员会看到PAPl系统指示的灯光信号颜色自靠近跑道向外依次为( )。A.白、红、红、红B.红、红、红、白C.白、白、白、
肾阳虚腰痛的主症特点是A.腰部刺痛,痛处固定B.腰膝冷痛,喜温喜按,遇劳更甚C.腰部隐痛,五心烦热D.热痛重着,活动后或可减轻E.腰部冷痛重着.转侧不利
某工程单代号网络图如下图所示,正确的说法是()。 A.工作D的ES为2B.工作G的FF为2C.工作H的FF为1D
会计除了核算和监督职能外,还有预测、决策、分析等职能。