it is pretty well understood what controls the flow of carbon dioxide in and out today.what 引导什么从句，it是不是形式主语，如果是形式主语可以用what吗，可不可以用that what？

how is it going 答语是pretty good 还是pretty well 翻译 It is not yet pretty well understood what made the rainforest disappear year by year. it is pretty,is not it? it pretty much is what it 英语翻译It is pretty well understood what controls the flow of carbon dioxide in and out the atmosphere today. why is she leaving?-well,it is pretty ,isnt it?A.clearly B.obvious C.suitable Dcertain 为什么不选A How is it going?pretty good it very pretty is 连词成句 It is well-known It is well You speak English pretty well.pretty前面为什么不加is? Now she plays it pretty well和The game was pretty good中为什么一个用good一个用well 英语,名词性从句 It is pretty well understood______controls the flow of carbon dioxide in and out the atmosphere today.答案是what ,为什么不能填that?为什么? It is pretty well understood____controls the flow of carbon dioxide in and out the atmosphere todayA.that B.when C.what D.how选什么理由? It is pretty well understood ___controls the flow of carbon dioxide in and out the atmosphere today填that what 还是what 为什么? 用pretty well造句 It's pretty good.对pretty good 提问 回答的格式是这样的 ( )is it（ this dress is pretty.ham much is it?答案