They had been talking when I arrived.这句话在语法上怎么解释?

They had been talking when I arrived.这句话在语法上怎么解释? 这句话,语法上怎么解释 改错：When I (A arrived) the station,the train (B had) (C been talking ,politely,l,arrived,when,they,were,with,each,other i haven't had a key这句话在语法上正确吗? They had done （most） work when I arrived.对括号内容提问 what do you think had happened to him. 这句话在语法上怎么用句 When they arrived there,they discovered that everything had 求英语高手You talking out the side of your neck这句话从语法上要怎么解释才通? It had been a very strange morning.这句话怎么分析?从语法句法角度 When they walking into the hall,they fall asleep.这句话从语法上看对吗 when i arrived california four months ago这句话有错吗?错在哪?急用!