________ tonuclear radiation, even for a short time, may produce variants(变异体)of genes in human bodies.A.BeingexposedB.HavingexposedC.ExposedD.Afterbeing exposed
网友回答
A解析注意到这道题中有一个插入语“ever for a short time”,可先去掉以便分析句子,插入语前面的是主语,必须用非谓语动词,再根据句意可知必须用被动语态。