LilyJune

这道题应该是C才对。
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants.
这句话说，herb是能生长在高金属土壤中植物的一种。
C说其他的others of the closely related group of plants 这种植物也生产 histidine ，那么可以推断 histidine也许是帮助这类型植物生活在高金属土的原因。