【题目】_____ to nuclear radiation, even for a short time, may produce variants (变异体) of genes in human bodies.
A. Exposed B. Being exposed
C. Having exposed D. After being exposed
在线课程【答案】B
【解析】
试题分析:考察动词非谓语形式。暴露在核辐射下，即使是很短的时间，都有可能造成基因的变异。该句中动名词短语作主语，又根据句意可知是被动，故选B。