【when引导时间状语从句的时态Everyone___quietwhentheconcert__(go/begin)用动词的正确形式填空They__formethenI___atthestation.(wait/arrive)答案是went,beganwerewaitingarrived为什么？】

　　when引导时间状语从句的时态

　　Everyone___quietwhentheconcert__(go/begin)用动词的正确形式填空

　　They__formethenI___atthestation.(wait/arrive)

　　答案是went,began

　　werewaitingarrived

　　为什么？