John didn't do his homework ____ his father came home from work.

A. unless　  B. while　  C. until　　  D. just as

昨日习题答案：

（ D. Having been ignored ） for many years, the writer suddenly became famous.

句意：这位作家被忽视了多年以后突然有了名气。 
现在分词短语作状语，表示时间。现在分词的逻辑主语也就是主句中的主语，所以用被动语态。