Researchers discovered that plants infected with a virus give off a gas that______disease resistance in neighboring plants.

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问题 Researchers discovered that plants infected with a virus give off a gas that______disease resistance in neighboring plants.

选项 A、contracts
B、activates
C、maintains
D、prescribes

答案B

解析 所填词需与disease resistance“抗病性”搭配,将[A]contract“感染”与[D]prescribe“开处方”先排除:[B]activates“激活、活化”与[C]maintains“保持”,发出的气体只能是“激活”抗病体而不是“保持”,所以答案为[B]。
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