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  3. Scientists have known for some time that certain plants, called hyperaccumu-lators, can concentrate minerals at levels a hundred

Scientists have known for some time that certain plants, called hyperaccumu-lators, can concentrate minerals at levels a hundred

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问题     Scientists have known for some time that certain plants, called hyperaccumu-lators, can concentrate minerals at levels a hundredfold or greater than normal. A survey of known hyperaccumulators identified that 75 percent of them amassed nickel; cobalt, copper, zinc, manganese, lead, and cadmium are other minerals of choice. Hyperaccumulators run the entire range of the plant world. They may be herbs, shrubs, or trees. Many members of the mustard family, spurge family, legume family, and grass family are top hyperaccumulators. Many are found in tropical and subtropical areas of the world, where accumulation of high concentrations of metals may afford some protection against plant-eating insects and microbial pathogens.
The word "afford" in the passage is closest in meaning to
选项 A、offer
B、prevent
C、increase
D、remove
答案A
解析
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