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。