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题库 / Prep2007E2-SC-56
Unlike crested wheatgrass, an alien species from Siberia that forms only shallow roots and produces tall above-ground shoots, native North American grasses develop an extensive root system, allowing for greater enrichment of the soil, but do not grow to be very tall.
native North American grasses develop an extensive root system, allowing for greater enrichment of the soil, but do not grow to be very
native North American grasses develop an extensive root system, which allows for their greater enrichment of the soil, but without growing to be that
the root system of native North American grasses is extensive, allowing for greater enrichment of the soil, but they do not grow to be very
the root system of native North American grasses is more extensive, allowing for the greater enrichment of the soil, but these grasses do not grow to be very
the extensiveness of the root system of native North American grasses allows for their greater enrichment of the soil, but they do not grow to be that
说的不对请大家指正。
B中的their可以refer到前面的grasses。但是它说：root system allows for greater enrichment，是整个development allow了greater enrichment，所以不是那么准确，选a。
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