prep 1-23~~求助！！

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.

(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

刚才找了一下讨论帖，其D答案跟我的不一样，是....and as sources of...

答案是E没有问题~~~可是为什么我这里的D选项错在哪里呢？我觉得有错，但又说不清楚~~~~

请教大家！！

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

and sources  作什么成分呢？ 句子主语  they 谓语动词应该复数

sources是名词吧~~~

我认为是forests 既提供了珍贵的药材，同时又提供了building material and firewood的sources,即把这两个名词并列~~

1）如果是按照LZ 说的两个名词并列,那么后面就是forests  supply sources of building material and firewood.

但是理解一下原句的意思，这里是 forests 是一个 source ，而不是提供了 source (如果是提供的话，那么这个 source of building material and firewood 是什么东东？

2）有句末现在分词做结果状语的，但是没见过 介宾结构在句末做的： for providing ...... 。如果按照LZ 理解，这个for 多余。