1. 英语主从复合句结构转换成汉语联合复句结构

　　1)The boy sat down on a stone to take a pebble out of his shoe when he saw a stranger approaching him.

　　小孩坐在石头上正打算从鞋里取碎石子，这时他看见一个陌生人朝着他走来。

　　2)Hardly had I got aboard when the train started.

　　我刚上火车，车就开了。

　　3)Our men had gone quite a distance off before the enemy's reinforcement troops came up.

　　我们的队伍已经走得很远了，敌人的增援部队才赶上来。