---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，他们结婚已是过去的事，那末，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。