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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】At noon on May 4th the carbon-dioxide concentration in the atmosphere around the Mauna Loa Observatory in Hawaii hit 400 parts per million(ppm). The average for the day was 399. 73 and researchers at ...
A.
CO 2 remains in the atmosphere for several dozen years.
B.
At current rates, Mauna Loa reading will rise above 450 ppm by 2075.
C.
The chance of cutting emissions and achieving 450 ppm by 2075 is good.
D.
Human"s gas emissions have been cut at once in order to achieve 450 ppm.
【单选题】我国首次发现的中新世鸟类，也是我国第一次发现的完整鸟化石，填补了我国第三纪鸟类化石空白的是（ ）
A.
秀丽杨氏鸟
B.
山旺山东鸟
C.
硕大临朐鸟
D.
硅藻中华河鸭
【单选题】At noon on May 4th the carbon-dioxide concentration in the atmosphere around the Mauna Loa Observatory in Hawaii hit 400 parts per million (ppm). The average for the day was 399.73 and researchers at ...
A.
Mauna Loa Observatory is located in northern Canada
B.
about 4 million years ago, jungles covered northern part of the Earth
C.
the carbon-dioxide concentration is expected to exceed 400ppm in the next few days
D.
it is the first time in human history that carbon-dioxide concentration reaches 400ppm