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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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Ron 大神讲解：
choice d:
- no comma after 'and', so sets up the expectation of parallelism. clearly there is no parallelism between 'supply potentially valuable pharmaceuticals' and 'as sources of building material and firewood', so that expectation is violated.
- 'for providing' makes no sense.
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