问题补充:
their homework, these three students have to stay in the classroom for another thirty minutes.
A. Not finishing
B. Not finished
C. Having not finished
D. Not having finished
答案:
A. Not finishing
B. Not finished
C. Having not finished
(答案→)D. Not having finished
解析:考查非谓语动词。句意:(由于)没有完成他们的作业,这些学生不得不在教室里再呆三十分钟。现在分词作原因状语表示正在进行的伴随性动作,如果动作发生在谓语动词之前,则用完成时态的过去分词,故选D。