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这句话的主语和谓语是：An investigation says，后面是宾语从句。宾语从句中含有so that结构。created in the United States after the September……是过去分词作后置定语，修饰system。
So… that…的意思是“如此地…以致于…”，它引导结果状语从句。在口语中，so…that…的that常被省去。例：
She felt so sad that tears came to her eyes．
她非常悲伤，泪水盈眶。
John was so drunk（that）he could not stand still．
约翰醉得站也站不住了。
He spoke so rapidly（that）we could hardly follow him．
他说得很快，我们很难听清楚他在说什么。
2.More than 250 government bodies have been created or reconstructed since 9.11, producing a system so complex and extensive that no one can be quite sure how much it costs or how effectively it works.
fairly, quite, rather, pretty用法区别
这四个词在用法上还有几点值得注意：
1)只有rather一词能和比较级及too连用, fairly, quite, pretty却不能。如：rather warmer, rather too sure(有点太自信)，quite可用在better前，指病完全好了。
2)quite和rather都可以用在冠词前，也可和动词连用，pretty和fairly则不能。如：quite a good film，rather a good idea, I quite like her.或I rather enjoy doing nothing.
3)quite, fairly,和rather也可放在a/an后，但名词前必须有形容词时。如：a quite good film, a fairly interesting lecture, a rather good idea。
4)一些“没有程度差别”的词，如：perfect, impossible, dead, 不能fairly, rather, pretty连用，但可以和quite连用，表示completely或absolutely(完全)的意思。如：quite exhausted(精疲力尽)，quite perfect（好极了）。
5)可以说：It’s quite the same. 但不能说：It’s not quite the same.
