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
68
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] After the key scientific fact was discovered, the scientists _____.
选项
A、felt it even harder to succeed in making synthetic diamonds
B、soon succeeded in changing cheap carbon into expensive diamonds
C、felt it more hopeful to succeed in making synthetic diamonds
D、found that carbon is very common in nature and so are diamonds
答案
C
解析
转载请注明原文地址:http://tihaiku.com/zcyy/3090553.html
相关试题推荐
Aspyistryingtosendasecretmessage,we’retryingtodecodehismessage,an
John:IwastryingtogetholdofJim,buthislinewasalwaysbusy...Sydney:
Aspyistryingtosendasecretmessage,we’retryingtodecodehismessage,an
______thecalculationisright,scientistscanneverbesurethattheyhaveincl
Aspyistryingtosendasecretmessage,we’retryingtodecodehismessage,an
Whatisscientists’aimofdrillingavolcano?[br][originaltext]16.Scientist
Whatisscientists’aimofdrillingavolcano?[br][originaltext]16.Scientist
Veryfewscientists______completelynewanswerstotheworld’sproblems.A、comeu
Scientistshavecuredcolorblindnessinmonkeysusinggenetherapy.As
Scientistshavecuredcolorblindnessinmonkeysusinggenetherapy.As
随机试题
[originaltext]Centuriesago,duringtheMiddleAges,mostofthelandinEur
Musicaffectsusasprofoundlyasanythingweexperience.Verymanypeoples
[originaltext][9]LastsummerIwentthroughatrainingprogramandbecame
消防水泵应确保从接到启泵信号到水泵正常运行的自动启动时间不应大于()。A.1
习近平新时代中国特色社会主义思想,明确中国特色社会主义事业战略布局是()。A.
B
心动周期中,心室血液的充盈主要取决于( )A.心房收缩的挤压作用 B.胸内负
老师想与同学处好关系,学生利用这一点在课上捣乱,怎么解决?
艾宾浩斯认为,遗忘的规律是()。A.先快后慢 B.先慢后快 C.匀速遗忘
检验批质量验收时,主控项目必须全部符合有关()的规定。A.工程监理规范 B.
最新回复
(
0
)