求问一个句子的语法，有关modifies！！！！！！！

karenalmn

曼哈顿语法第四章modifies里有个句子
WRONG: Citizens of many countries are expressing concern about the environmental damage caused by the widespread release of greenhouse gases may be impossible to reverse.
RIGHT: Citizens of many countries are expressing concern THAT the environmental damage caused by the widespread release of greenhouse gases may be impossible to reverse.原因是： Citizens of many countries are expressing concern about the environmental damage caused by the widespread release of greenhouse gases 并没有错，但后面may be impossible to reverse 没有主语，前句的environmental damage是prepositional phrase（即about。。。。）的一部分，所以该名词没法当主语。因此将about改成that。

然后这里想很蠢的问个问题， caused by the widespread release of greenhouse gases这句话不是一个noun modifier 修饰environmental damage吗？如果about的情况下environmental damage 不能当subject,那么划线这个caused...是在修饰什么？
有点钻牛角尖学迷糊了，但还是求大神解答

fxxxfxxx

没有that就没有从句，那又何来主语呢。

mazarstax

小弟愚見係:-

Citizens of many countries [S] are expressing [V] concern about the environmental damage caused by the widespread release of greenhouse gases [O] may be [V] impossible to reverse [O].

可能有少少亂, 如果是about的話,整句結構就會是S V O V O
如果是That 的話,整句結構就會是S V conjunction S V O.

其實我都是自己猜想, 剛開始準備GMAT