It is pretty well understood ________ controls the flow of carbon dioxide in and out the atmosphere ...
2022-11-25 16:48:19 187次 2014年高考考点模拟训练及真题研练（12）时态与语态英语试卷（解析版） 单项填空 反馈错误 加入收藏 正确率 : 100%
题目内容：
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
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