they (know)each other since they (begin) to work in that factry.

题目

they (know)each other since they (begin) to work in that factry.
请问正确时态是什么呢?1.knew.began.2.have known.began.3.had konwn.began.

答案

2在这里since从句后面谓语动词用一般过去时,主句用现在完成时这里有一些例句,可以看一下然后理解一下1) since +过去一个时间点 (如具体的年、月、日期、钟点、1980,last month,half past six).I have been here sinc...