ResearcherssaytheEarthhadmuchmoreoxygen(氧气)nearlyabilli...

问题详情：

Researchers say the Earth had much more oxygen(氧气) nearly a billion years ago than scientific experts thought. That claim could change theories（理论） about how life developed on our planet.

    The claim came from researchers at Brock University in Canada. They wanted to measure the levels of oxygen in the Earth's atmosphere nearly a billion years ago. To do this, the researchers developed a way to study small air bubbles（气泡） trapped in ancient salt crystals（结晶；晶体）.

    "There was a lot of debate as to what the oxygen content was 800 million or more years ago," said Nigel Blamey of Brock University's Department of Earth Sciences. He said the trapped gases showed that the oxygen level was about half of what it is today.

    By analyzing（分析） tiny air bubbles in halite, researchers determines（查明；测定；确认） ancient Earth had much more oxygen than previously thought. In fact, many experts believed that the oxygen level was only about two percent of the atmosphere so long ago. But the new study found that it was almost 11 percent. Currently, oxygen is about 21 percent of the atmosphere.

    The Canadian researchers used a method（方法） to study air bubbles trapped in halite, the natural form of table salt.

    The researchers say their findings have major effects for theories about how and when life developed.

    Professor of Earth Sciences Uwe Brand said that higher oxygen levels in the past may turn back the clock when complex life developed. "Now paleobiologists（古生物学家）will have reason to go looking for rocks with" evidence of these first evolutionary（进化的） steps," he told the Canadian Broadcasting Corporation.

word“claim”in Paragraph 1 means_________ in Chinese.

A.说法           B.建议          C.目标         D.目的

oxygen makes up about_______ of the atmosphere.

  A.9 percent.        B.10 percent.      C.11 percent.   D. 21 percent

h of the following statements is False?

A. Some researchers wanted to measure the levels of oxygen in the Earth's atmosphere nearly a billion years ago.

B. Among scientists, there was a lot of debate as to what the oxygen content was 800 million or more years ago.

C. In fact, many experts believed that the oxygen level was only about eleven percent of the atmosphere so long ago

D. The researchers say their findings have major effects for theories about how and when life developed.

the article, we know that the researchers came from____________.

A. Oxford University        B. Cambridge University

C. Peking University        D. Brock University

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