![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
According to the earlier study, the Earth hasn't warmed as expected because______.
A.
the amount of greenhouse gases released is quite small
B.
people are not sensitive to the change of the climate
C.
its climate may not be that sensitive to greenhouse gases
D.
water vapor in the stratosphere has increased sharply