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Which of the following most logically completes the argument? A certain cultivated plant is part of a family of species that flourish in soils rich in heavy metals that are harmful to most other plants. Researchers examining this plant have found that it generates significant amounts of arginine, an amino acid that, in laboratory tests, neutralizes these metals. Therefore, it is possible that the plant's high arginine production enables it to thrive in metal-laden soils, a theory that would be supported if ______.