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.
Pharmaceutical制药品
(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 好像这道题每人讨论过啊，能否有高手指正？感激不尽 作者: kikisunflower 时间: 2011-5-8 22:22
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句子结构： while they do A, do B and do C, the forests also supply...and provide...