【题目】_________to nuclear radiation, even for a short time, may produce variants of genes in human bodies.
A. Being close B. Having been closed
C. Closed D. After being closed
在线课程【答案】A
【解析】考查非谓语动词。句意：靠近核辐射，甚至在很短的时间，可能在人体内产生基因变异。分析句子结构，空格处是作主语，故要用动名词形式，故选A。