PREP-1-23 破解版的分析不太理解，多谢指点！

23.   (25773-!-item-!-188;#058&002128)  

While they remove carbon dioxide from the air, conserve soil and water, and house thousands of species, forests also supply potentially valuable pharmaceuticals, and, as sources of building material and firewood, that provide employment for millions worldwide[BryanZhou1] .

(A) pharmaceuticals, and, as sources of building material and firewood, that provide

(B) pharmaceuticals, and sources of building material and firewood, are providers of

(C) pharmaceuticals and, as sources of building material and firewood that are providing

(D) pharmaceuticals and sources of building material and firewood, for providing

(E) pharmaceuticals and, as sources of building material and firewood, provide

D意思是，森林提供医药和建筑材料的sources？应该是作为建筑材料的sources.

for providing做什么成分？如果没有插入语，forests also supply potentially valuable pharmaceuticals, providing ...我觉得也对

请问D这里for providing没有错么？谢谢！

同问，同问！！

好像E违反平行了哦, 这个似乎是更严重的错误

所以用排除法只有D了

再说下, for doing 并不是不可以的, 可以表用途

a knife for cutting 是某个CD NN 举的例子

好像是比较模糊。

整个句子结构：D： while xx do, do, and do, xx also do sth and sth , for providing...

              E:  while xx do, do, and do, xx also do sth  and (插入语) provide..

D选项 for 前面还加了comma，作为状语成分，for 表目的 为了提供就业就会 而供应这些东西 好像说不通。

个人倾向于选E 不知各位NN高见。