提问：用一般过去时或过去进行时填空大神们帮帮忙

提问：用一般过去时或过去进行时填空大神们帮帮忙
例：1.We were leaving (leave) the house when the postman arrived.2．She dropped some money just as she______（ get off）the bus.3.Someone______(ring)while I was working in the garden.比如说第一题,我认为“were leaving the house”和“when the postman arrived”是同时在过去进行的动作,都应该用过去进行时.“当邮递员到达时”（这算是一个正进行的动作）我们在干嘛呢?我们正要离开房子.正解却不是我这样理解的,