【题目】—How long _____each other before they _____here?
—For about a year.
A. have they known, come B. did they know, came
C. do they know, come D. had they known, came
在线课程【答案】D
【解析】
考查时态。句意：—他们来这儿之前认识多久了？—大约一年了。根据句意分析，他们来到这里是过去的事，他们互相了解大约一年的时间肯定发生在来这里之前，发生在过去某一动作之前的动作，应该使用过去完成时。故D选项正确。