--How long each other before they married?
--For about a year.
A. have they known;get
B. did they know; were going to get
C. do they know;are going to get
D. had they known; got
网友回答
A. have they known;get
B. did they know; were going to get
C. do they know;are going to get
(答案→)D. had they known; got
解析：
根据句意分析，他们结婚是已过去的事，那么，他们互相了解大约一年的时间肯定发生在结婚前，发生在过去某一动作之前的动作，应该使用过去完成时。