课程咨询

GRE首页 GRE课程 GRE动态 0元讲座 GRE模考网站

新东方在线 > GRE > GRE阅读 > 正文
扫码关注掌握一手留学资讯

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

2016年GRE阅读答案(23)

2015-11-27 15:22:13来源：网络

　　When Earth formed 4.6 billion years ago, the Sun burned only 70 percent as brightly as it does today. Yet Geologic record contains no evidence for widespread glaciation until 2.3 billion years ago. Sagan and Mullen suggested in the 1970s that ammonia, a greenhouse gas, warmed early Earth’s atmosphere, but subsequent research showed that the Sun’s ultraviolet rays rapidly destroy ammonia in an oxygen-free environment, such as that of early Earth. Many scientists now attribute much of the warming of early Earth to oxygen-intolerant microbes—methanogens—that produce the greenhouse gas methane. The methanogen hypothesis could help to explain the first global ice age: 2.3 billion years ago, Earth’s atmosphere began to fill with oxygen produced by other microbes—cyanobacteria—causing methanogens to decline rapidly.

　　1. Which of the following best describes the function of the highlighted sentence?

　　A. It refutes the possibility of a connection between two events previously thought to be related.

　　B. It describes how a hypothesis might account for the timing of a phenomenon described earlier in the passage

　　C. It presents evidence that casts doubt on a statement made in the first sentence of the passage

　　D. It clarifies a distinction between two related hypotheses

　　E. It introduces findings that challenge a dominant explanation for a particular phenomenon

　　2. Which of the following can be inferred from the passage about methanogens?

　　A. Methanogens must have appeared on Earth later than 2.3 billion years ago.

　　B. Methanogens must have been much more prevalent in some regions of the early Earth than in others.

　　C. Methanogens produce a greenhouse gas that is more susceptible to destruction by the Sun’s ultraviolent rays than is ammonia.

　　D. Methanogens could not have thrived in early Earth’s atmosphere without the presence of ammonia.

　　E. Methanogens would have had a less significant effect on early Earth’s atmosphere if they had evolved after the appearance of cyanobacteria.

　　本篇GRE阅读答案见下一页：

本文关键字: GRE阅读 GRE真题 GRE机经

上一页 1 2 下一页

添加新东方美研助教回复【GRE】获取

模考真题|写作题库|阅读机经|佛脚词汇

更多资料

添加美研助教号，
回复【GRE】获取备考必看资料包

  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加美研助教号】，回复对应关键字领取学习资料。
更多>>
更多内容

关注新东方美研助教

回复【GRE】获取备考必看资料包

新东方美研备考资料
GRE录播课（全科班/单项班） GMAT6-8人直播VIP小班 托福直播精讲班（30天/60天）
更多>>
更多惊喜>>

添加美研助教号，
回复【GRE】获取备考必看资料包

  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加美研助教号】，回复对应关键字领取学习资料。
更多>>
更多资料
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10