【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：考查动名词作主语。being exposed to nuclear radiation为动名词短语作主语。本句意为：暴露在核辐射下，甚至是一小会，都会导致人体内基因的变异。故选B。