问题
选择题
It is pretty well understood _____ controls the flow of carbon dioxide in and out the atmosphere today. [ ]
A. that
B. when
C. what
D. how
答案
答案：C
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It is pretty well understood _____ controls the flow of carbon dioxide in and out the atmosphere today. [ ]
A. that
B. when
C. what
D. how
答案：C