题干
. It is pretty well understood ________ controls the flow of carbon dioxide in and out the atmosphere today.
A：that
B：that what
C：what
D：how
答案(点此获取答案解析）
C
A：that
B：that what
C：what
D：how
3C(气), 在一定的条件下, 使一定量A和B气体反应, 达到平衡状态时, 具有的性质是: ( )