David offered us a lift when he was leaving the office,but our word---?---,we declined the offer.

问题描述:

David offered us a lift when he was leaving the office,but our word---?---,we declined the offer.
A,not being finished B,not having finished
C,had not been finished D,was not finished

答案是:B
译为现在的事情还没有做完,还在进行,而且是被动的时态.