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题库 / Prep2007E1-SC-23
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.
pharmaceuticals, and, as sources of building material and firewood, that provide
pharmaceuticals, and sources of building material and firewood, are providers of
pharmaceuticals and, as sources of building material and firewood that are providing
pharmaceuticals and sources of building material and firewood, for providing
pharmaceuticals and, as sources of building material and firewood, provide
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forest可以supply building material，但不能supply sources of building material，只能as sources of material。我是这么理解的……。而且如果for providing（这个for也很可疑）放在后面的话，用做药材这个用处也可以提供employment了，但并不make sense。
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