Question

【题目】Potatoes turn green when ________ to light.

A. exposed B. are exposed

C. being exposed D. to be exposed

Answer 1

【答案】A

【解析】

试题分析：考查非谓语动词。be exposed to遭受，暴露于…，这里的exposed可以看作 when they are exposed to the light的省略。因为句子中有when,while等这些词时，从句可以省略与主句相同的主语和be动词。是使显露的意思。故选A。