首页
登录
职称英语
Over the centuries, scientists have been trying hard to find satisfactory su
Over the centuries, scientists have been trying hard to find satisfactory su
游客
2023-10-11
37
管理
问题
Over the centuries, scientists have been trying hard to find satisfactory substitutes for precious stones but failed many times.
Many years ago, a chemist surprised the world by saying: It should be possible to make a precious stone that not only looks like the real thing, but that is the real thing.The only difference should be that one crystal would be made by man, the other by nature.
At first this did not seem like a particularly hard task.
Scientists began to try making synthetic diamonds towards the end of the eighteenth century and discovered a key scientific fact
: diamonds are a form of carbon, which is a very common element.
Then, why not change a cheap and plentiful substance, carbon, into a rare and expensive one, diamond?This change takes place in nature, so it should be possible to make it happen in the laboratory.
It should be possible, but for 150 years every effort failed though several people believed that they had solved the diamond riddle during this period.
The real success came after the scientists realized that, in changing carbon into diamonds, unbelievably heavy pressure and extremely high temperature are indispensable, and carbon needs to be dissolved(溶解) in a metal that helps the reaction to take place more easily.
Under these conditions, a number of shiny crystals were produced in the laboratories of the General Electric Company.The results of careful analysis showed that the chemist was right: these jewels of the laboratory were not like diamonds; they were diamonds. [br] According to the passage, the real success probably came _____.
选项
A、in the 19th century
B、around 1900
C、150 years ago
D、around 1950s
答案
D
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3090554.html
相关试题推荐
Veryfewscientists______completelynewanswerstotheworld’sproblems.A、comeu
Scientistshavecuredcolorblindnessinmonkeysusinggenetherapy.As
Scientistshaveidentifiedthelikelyculpritinadiseasethathasdevastat
Scientistshaveidentifiedthelikelyculpritinadiseasethathasdevastat
Ateamofscientistshasjustfinishedwhatmightliterallybedescribedas
Ateamofscientistshasjustfinishedwhatmightliterallybedescribedas
Ateamofscientistshasjustfinishedwhatmightliterallybedescribedas
Ateamofscientistshasjustfinishedwhatmightliterallybedescribedas
_______thecalculationisright,scientistscanneverbesurethattheyhavein
Aspyistryingtosendasecretmessage,we’retryingtodecodehismessage,an
随机试题
Youcanhave______paiddirectfromyouraccount.[br][originaltext]Presente
It’snosecretthatscrollingthroughendlessimagesandannouncementsof
TheHistoryofChineseAmericans[A]ChinesehavebeenintheUnitedStat
Accustomedthoughwearetospeakingofthefilmsmadebefore1927as"silent
简述教育的相对独立性的表现。
可导致卟啉代谢紊乱,使血红蛋白合成受抑的是A.PbB.HgC.CdD.AlE.A
新投运和解体检修后的设备,应在投运后3个月内进行一次运行电压下的检测。()
2021年一季度,规模以上工业原油产量同比增长:A.低于0.4% B.0.
语文老师想在课上播放《老师难忘的记忆》视频。录制时各科老师纷纷响应,都来帮忙,这
患者,女性,50岁。对称性多关节肿痛伴晨僵1年余,血RF1:40(+),ESR1
最新回复
(
0
)