选课中心
7099人选课
GRE公开讲座
0元
GMAT公开讲座
0元
一对一体验课
99元
GRE模考网站
10000人
托福TPO模考网站HOT
39209人预约
GRE辅导课程
17537 人
GMAT辅导课程
17537 人
托福辅导课程
17537 人
【定制】1v1
私人订制
资料下载
考前冲刺
扫码关注掌握一手留学资讯
回复XDF免费领
水平测试和备考资料
扫码关注公众号
GRE阅读复习中,大家想要提高阅读速度,其实最好的方法就是利用真题来进行练习,通过真题的练习,大家能够更好地了解自己在备考中的不足,更好地备考GRE阅读考试。下面就是详细的内容整理!
Until recently astronomers have been puzzled by the fate of red giant and supergiant stars. When the core of a giant star whose mass surpasses 1.4 times the present mass of our Sun (M) exhausts its nuclear fuel, it is unable to support its own weight and collapses into a tiny neutron star. The gravitational energy released during this implosion of the core blows off the remainder of the star in a gigantic explosion, or a supernova. Since around 50 percent of all stars are believed to begin their lives with masses greater than 1.4M, we might expect that one out of every two stars would die as a supernova. But in fact, only one star in thirty dies such a violent death. The rest expire much more peacefully as planetary nebulas. Apparently most massive stars manage to lose sufficient material that their masses drop below the critical value of 1.4 Mbefore they exhaust their nuclear fuel. Evidence supporting this view comes from observations of IRC+10216, a pulsating giant star located 700 light- years away from Earth. A huge rate of mass loss (1 M every 10,000 years) has been deduced from infrared observations of ammonia (NH3) molecules located in the circumstellar cloud around IRC+10216. Recent microwave observations of carbon monoxide (CO) molecules indicate a similar rate of mass loss and demonstrate that the escaping material extends outward from the star for a distance of at least one light-year. Because we know the size of the cloud around IRC+10216 and can use our observations of either NH3 or CO to measure the outflow velocity, we can calculate an age for the circumstellar cloud. IRC+10216 has apparently expelled, in the form of molecules and dust grains, a mass equal to that of our entire Sun within the past ten thousand years. This implies that some stars can shed huge amounts of matter very quickly and thus may never expire as supernovas. Theoretical models as well as statistics on supernovas and planetary nebulas suggest that stars that begin their lives with masses around 6 M shed sufficient material to drop below the critical value of 1.4M.IRC+10216, for example, should do this in a mere 50,000 years from its birth, only an instant in the life of a star.
But what place does IRC+10216 have in stellar evolution? Astronomers suggest that stars like IRC+10216 are actually "protoplanetary nebulas" –old giant stars whose dense cores have almost but not quite rid them. Once the star has lost the entire envelope, its exposed core becomes the central star of the planetary nebula and heats and ionizes the last vestiges of the envelope as it flows away into space. This configuration a full-fledged planetary nebula, long familiar to optical astronomers.
The primary purpose of the passage is to
A.offer a method of calculating the age of circumstellar clouds
B.describe the conditions that result in a star's expiring as a supernova
C.discuss new evidence concerning the composition of planetary nebulas
D.explain why fewer stars than predicted expire as supernovas
E.survey conflicting theories concerning the composition of circumstellar clouds
The view to which line 18 refers serves to
A.reconcile seemingly contradictory facts
B.undermine a previously held theory
C.take into account data previously held to be insignificant
D.resolve a controversy
E.question new methods of gathering data
It can be inferred from the passage that the author assumes which of the following in the discussion of the rate at which IRC+10216 loses mass?
A.The circumstellar cloud surrounding IRC+10216 consists only of CO and NH3 molecules.
B.The circumstellar cloud surrounding IRC+10216 consists of material expelled from that star.
C.The age of a star is equal to that of its circumstellar cloud.
D.The rate at which IRC+10216 loss mass varies significantly from year to year.
E.Stars with a mass greater than 6M lose mass at a rate faster than stars with a mass less than 6 M do.
According to information provided by the passage, which of the following stars would astronomers most likely describe as a planetary nebula?
A.A star that began its life with a mass of 5.5 M, has exhausted its nuclear fuel, and has a core that is visible to astronomers
B.A star that began its life with a mass of 6 M, lost mass at a rate of 1 M per 10,000 years, and exhausted its nuclear fuel in 40,000 years
C.A star that has exhausted its nuclear fuel, has a mass of 1.2 M, and is surrounded by a circumstellar cloud that obscures its core from view
D.A star that began its life with a mass greater than 6 M, has just recently exhausted its nuclear fuel, and is in the process of releasing massive amounts of gravitational energy
E.A star that began its life with a mass of 5.5 M, has yet to exhaust its nuclear fuel, and exhibits a rate of mass loss similar to that of IRC+10216
Which of the following statements would be most likely to follow the last sentence of the passage?
A.Supernovas are not necessarily the most spectacular events that astronomers have occasion to observe.
B.Apparently, stars that have a mass of greater than 6 M are somewhat rare.
C.Recent studies of CO and NH3 in the circumstellar clouds of stars similar to IRC+10216 have led astronomers to believe that the formation of planetary nebulas precedes the development of supernovas.
D.It appears, then, that IRC+10216 actually represents an intermediate step in the evolution of a giant star into a planetary nebula.
E.Astronomers have yet to develop a consistently accurate method for measuring the rate at which a star exhausts its nuclear fuel
Which of the following titles best summarizes the content of the passage?
A.New Methods of Calculating the Age of Circumstellar Clouds
B.New Evidence Concerning the Composition of Planetary Nebulas
C.Protoplanetary Neula: A Rarely Observed Phenomenon
D.Planetary Nebulas: An Enigma to Astronomers
E.The Diminution of a Star's Mass: A Crucial Factor in Stellar Evolution
正确答案:D A B A D E
以上就是关于“GRE阅读模拟在线练习附答案一百二十一”的内容,更多精彩内容,请关注GRE频道!
2月GRE公开课,助力GRE备考-1元抢报!
资料下载
GRE佛脚2024增补包含最新热词与六选二整理
发布时间:2022-06-06添加新东方在线美研助教号
回复【资料】获取
GRE-PPO模考完整套题+解析资料下载
发布时间:2022-06-06添加新东方在线美研助教号
回复【资料】获取
GRE佛脚词汇表网络版资料下载
发布时间:2022-05-21添加新东方在线美研助教号
回复【资料】获取
2024GRE佛脚填空机经系列资料下载
发布时间:2022-04-15添加新东方在线美研助教号
回复【资料】获取
2024GRE佛脚阅读系列资料下载
发布时间:2022-04-15添加新东方在线美研助教号
回复【资料】获取
2024杨鹏阅读难句(GMAT+GRE)教程资料下载
发布时间:2022-04-15添加新东方在线美研助教号
回复【资料】获取
GRE PPO模考完整练习题(答案)
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
GRE写作题库解析【Issue/Argument】
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
GRE阅读机经及官方真题资料练习
发布时间:2019-12-10关注新东方在线美研订阅号
回复【GRE】获取
GRE填空机经佛脚系列资料持续更新…
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
GRE佛脚词汇修订版PDF电子版下载
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
【提升英语必看】英语记录片/演讲/美剧合集
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
《华尔街日报》、《纽约时报》英文报刊合集
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
【必看】美国研究生申请注意事项
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
美国研究生录取分数&截止日期信息汇总
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
2020美国研究生热门专业院校排名
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
GRE模考套题、机经汇总
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
添加美研助教号,
回复【GRE】获取备考必看资料包
推荐阅读
更多>>为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读的命题规则,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读的排除法,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GRE
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读高分备考攻略,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读的做题思路,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读考试的相关技巧,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读合理分配好时间,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读考试的心态,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读考试的常见题型,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读长难句的语法介绍,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读规律的介绍,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
添加美研助教号,
回复【GRE】获取备考必看资料包
资料下载
更多>>添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
关注新东方在线美研订阅号
回复【GRE】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
阅读排行榜
相关内容