Question

________ tonuclear radiation, even for a short time, may produce variants（变异体）of genes in human bodies.

1. A.
   Beingexposed
2. B.
   Havingexposed
3. C.
   Exposed
4. D.
   Afterbeing exposed

Answer 1

A
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。