问题补充:
The old man, abroad for twenty years, is on the way back to his motherland.
A. to work
B. working
C. to have worked
D. having worked
答案:
A. to work
B. working
C. to have worked
(答案→)D. having worked
解析:本题考非谓语动词。句中两个逗号中间的内容应是时间状语,故全句解释为:在国外工作了二十年后,这位老人(已动身)正在归国途中。不定式作状语,多表目的和结果,不合句意,排除A、C,分词作状语可表时间、方式、伴随。此处是已完成的主动的动作,不是正在进行当中的主动动作,所以排除B,选D,现在分词完成式表主动和完成(到谓语发生时,非谓语的动作已完成)。