We can learn from the first paragraph that______. 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 400 ppm in the next few days D．it is the first time in human history that carbon-dioxide concentration reaches 400 ppm
A. A．Mauna B.about C.the D.it
【参考答案】
C 根据选项[A]中的MaunaLoa定位到首句：．．．theMannaLoaObservatoryinHawa......