求英语高手帮我看下90考研英语的长难句。

Question

The surface temperature of Venus reaches some 900F. ②Added to that is an atmospheric pressure about 90 times Earth’s: High overhead in the carbon dioxide (CO2) that passes for air is a layer of clouds, perhaps 10 to 20 miles thick, whose little drops consist mostly of sulfuric acid (H2SO4).。。。。第一句没问题。第二句ADDed开始。。倒装了？倒装的原因是啥？ 第二个问题。那个 passes for air 的pass做什么解释。。第三个问题。。, whose little drops consist mostly of sulfuric acid (H2SO4).。这里的little drops 我开始理解成小雨滴。。答案的翻译是高空中被看作是空气的二氧化碳形成了一层厚约10到20 公里的浓云，而浓云的主要成分为硫酸。这里怎么成了浓云？
High overhead in the carbon dioxide (CO2) that passes for air is a layer of clouds这句不懂。in the CO2是什么意思 在二氧化碳中被当做氧气？

Answer 1

第一个问题:
不是倒装. 是省略句。
Added to that is an atmospheric pressure about 90 times Earth’s.
=What is added to that is an atmospheric pressure about 90 times Earth’s.
that 代表前一句所述的事实。

第二个问题:
pass for是个短语，意思是: 被当作
如:A great man's foolish sayings pass for wise ones. 一个大人物的傻话会被当作明智的格言。
It might easily pass for silk.它很容易被当成丝绸。

第三个问题:
尽管little drops是从浓云而来, 你把little drops翻成小雨滴更贴近原文。

补充问题：
被当成‘空气’的由二氧化碳组成的高大悬浮体其实是一层厚达...

High overhead in the carbon dioxide (CO2) that passes for air is a layer of clouds这句不懂。in the CO2是什么意思 在二氧化碳中被当做氧气？追问

屌爆了！！太厉害了！！！。高手 膜拜。。最后一问。High overhead in the carbon dioxide (CO2) that passes for air is a layer of clouds 这句应该是倒装了吧？这句正常语序应该怎么样？还是说我又理解错了。