问题
选择题
--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
答案
答案：D
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。