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
专升本
For many years, scientists couldn’t figure out how atoms and molecules(分子)on the Earth combined to make living things. Plants, f
For many years, scientists couldn’t figure out how atoms and molecules(分子)on the Earth combined to make living things. Plants, f
admin
2014-05-25
47
问题
For many years, scientists couldn’t figure out how atoms and molecules(分子)on the Earth combined to make living things. Plants, fishes, dinosaurs(恐龙), and people are made of atoms and molecules, but they are put together in a more complicated way than the molecules in the primitive ocean. What’s more, living things, that have energy and can reproduce on the Earth four billion years ago were lifeless.
After years of study, scientists figured out that living things, including human bodies, are basically made of amino acids and nucleotide(氨基酸与核苷酸)bases. These are molecules with millions of hydrogen(氢), carbon(碳), nitrogen(氮), and oxygen atom. How could such complicated molecules have been formed in the primitive soup? Scientists were stumped(难住).
Then, in 1953, two scientists named Harold Urey and Stanley L. Miller did a very simple experiment to find out what had happened on the primitive Earth. They set up some tubes and bottles in a closed loop(线圈), and put in some of the same gases that were present in the atmosphere four billion years ago: water vapor, carbon dioxide(二氧化碳), methane(甲烷), and hydrogen.
Then they shot an electric spark through the gases to simulate(模拟)bolts(闪电)of lightning on the ancient Earth, circulated the gases through some water, sent them back for more sparks, and so on. After seven days, the water that the gases had been bubbling(起跑)through had turned brown. Some new chemicals were dissolved in it . When Miller and Urey analyzed the liquid, they found that it contained amino acids—the very kind of molecules found in all living things.
At the end of the last paragraph, the word "it" refers to______.
选项
A、a close loop
B、an electric spark
C、water
D、the liquid
答案
D
解析
文章最后一句话when Miller and Urey analyzed the liquid,they found thatit contained…,“当他们对液体进行分析时,发现里面含有……”中得知,it指的就是从句中的liquid。
转载请注明原文地址:https://kaotiyun.com/show/rFUC777K
本试题收录于:
英语题库普高专升本分类
0
英语
普高专升本
相关试题推荐
Iknowit’snotimportantbutIcan’thelp______aboutit.
Theconditionbeing______,hemaysucceed.
Mostpeopleretirefromworkbetweentheagesof60and65.Thishas【31】consequences,oneeconomicand【32】psychological.Eco
Itisnot______todiscussthequestionagainandagain.
Hefailedinthisexam,______provesthathewasn’tworkinghardenough.
ThatwassoseriousamatterthatIhadnochoicebut______thepolice.
Extensivereportingontelevisionhashelpedto______interestinawidevarietyofsportsandactivities.
"WasthedrivingpleasantwhenyouvacationedinMexicolastsummer?"No,it_____forfourdayswhenwearrived,sotheroadswer
66)Timespentinawell-decoratedbookshopcanbemostenjoyable,whetheryouareakeenbook-loverormerelytheretobuyanic
随机试题
Hehasbeencalledthe"missinglink".Half-man,half-beast.Heissupposedtoliveinthehighestmountainintheworld—MountE
关于外生殖器发生的描述正确的是
下列关于基本医疗保险品种目录的说法,错误的是
设总体X~N(μ,σ12),Y~N(μ2σ2,2),检验假设H0:σ12=σ22;H1:σ12≠σ22;α=0.10,从C中抽取容量为n1=12的样本,从Y中抽取容量为n2=10的样本,算得s12=118.4,s22=31.93,正确的检验方法与结论是(
顶管采用于工掘进顶进时,应符合下列()的规定。
某预应力混凝土简支梁桥,总体立面布置如图28313010一1所示(尺寸单位:m),则该桥的全长、多跨径总长和计算跨径分别是()。[2011年真题]
同业拆借市场的功能包括()。
填制凭证时发生错误,应该采取()进行更正。
常见的定价方法包括()。
国家征收教育附加费的行为属于()。
最新回复
(
0
)