首页
登录
职称英语
[originaltext] Diamonds are the hardest substance known on Earth and they ma
[originaltext] Diamonds are the hardest substance known on Earth and they ma
游客
2024-04-26
8
管理
问题
Diamonds are the hardest substance known on Earth and they make sparkling jewelry as well as saw blades that can cut through pretty much anything.
Recently, geologists studying diamonds have identified the ages of thousands of diamonds from Southern Africa, where the mineral is most abundant. Their research found that there were only three times in Earth’s history when diamonds were made and that Earth no longer makes diamonds like it used to. "Something was different then. Perhaps the planet was hotter on the inside, or the composition of the rocks was subtly different. Whatever it was it has changed now," stated Steve Shirey, of the Carnegie Institution in Washington, D.C., one of the project researchers.
The oldest diamonds were made 3.3 billion years ago when Earth was relatively young. The second time diamonds formed was 2.9 billion years ago. Small bits of rock within those diamonds, called impurities, indicate that they probably formed from rocks laid down in a shallow sea suggesting that the carbon that made the diamonds probably came from the remains of ancient sea life. The youngest diamonds on Earth are 1.2 billion years old although a few smaller diamonds are about 100 million years old.
Some people like diamonds because they are pretty, rare, or expensive but Dr. Steve Shirey has a different perspective. "I think of diamonds," he said, "as being tiny time capsules that encase a little piece of rock protecting it for billions of years and providing us with a unique window on ancient times."
19. What does the speaker tell us about diamonds?
20. What does the speaker want to convey by the remarks of Steve Shirey?
21. According to the speaker, when were the youngest diamonds made?
选项
A、They were made only three times in Earth’s history.
B、The most beautiful diamond comes from Africa.
C、They are even harder than those saw blades.
D、The hardness of diamonds depends on the purity.
答案
A
解析
文中提到“研究发现,钻石只在地球历史的三个时期形成”。A项为正确答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3571401.html
相关试题推荐
[originaltext]Themostimportantmessagethathumansdelivertooneanother
[originaltext]AmericanIndiansgrewandsmokedtobaccobeforeColumbuscame
[originaltext]AmericanIndiansgrewandsmokedtobaccobeforeColumbuscame
[originaltext]W:Whatdidyouthinkaboutthemovie?M:Well...IthinkHarryP
[originaltext]W:Whatdidyouthinkaboutthemovie?M:Well...IthinkHarryP
[originaltext]W:Whatdidyouthinkaboutthemovie?M:Well...IthinkHarryP
[originaltext]M:First,Iwanttothankyouforagreeingtothissurvey.Thisi
[originaltext]M:First,Iwanttothankyouforagreeingtothissurvey.Thisi
[originaltext]M:First,Iwanttothankyouforagreeingtothissurvey.Thisi
[originaltext]W:Canyoudropbythelabforaminute?Ihavesomeexperiments
随机试题
TheUnitedStatesranksfirstamongWesterncountriesasfarasdivorcerateis
[originaltext]TheAmericansbelievethatanybodycanbecomePresidentofthe
Virusesarehuman-madesoftwareprograms【C1】______specificallytowreakhavo
有关城镇垃圾转运量小于150t/d的小型转运站的设置标准,以下哪项不正确?(
用1%麻黄素液滴鼻的主要目的是()A:收缩血管,减轻炎症反应 B:收缩血管,
某兴趣小组中,所有人都喜欢吃苹果、梨、香蕉中的至少一种水果。经统计,喜欢吃香蕉的
禁止对特定纳税人给予歧视性对待,也禁止在没有正当理由的情况下对特定纳税人给予特别
某研究者欲了解某地正常成年男性和女性的红细胞总体平均水平是否有差异,随机抽样测定
二尖瓣狭窄A.心尖部舒张中晚期隆隆样杂音 B.胸骨左缘3肋问舒张期叹气样杂音
对建设周期一年半以上的工程项目,采用变动总价合同时,应考虑引起价格变化的因素有(
最新回复
(
0
)