问题
选择题
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
D
此题考查非谓语动词形式如何体现时间顺序。不定式表将来、打算；动词ing形式表主动、进行；由于已经工作20年，所以选D项。