请教老师：

这是新概念2-48课：

Dentists always ask questions when it is impossible for you to answer. My dentist had just pulled out one of my teeth and had told me to rest for a while. I tried to say something, but my mouth was full of cotton wool. He knew I collected match boxes and asked me whether my collection was growing. He then asked me how my brother was and whether I liked my new job in London. In answer to these questions I either nodded or made strange noises. Meanwhile, my tongue was busy searching out the hole where the tooth had been. I suddenly felt very worried, but could not say anything. When the dentist at last removed the cotton wool from my mouth, I was able to tell him that he had pulled out the wrong tooth.

看上面课文中的一句话：

He knew I collected match boxes and asked me whether my collection was growing.

1）我注意到collected 和 was growing 2种不同的时态。

一般过去时是否既可以表示做过某事（动作结束），也可表示过去的习惯（过去经常性的行为）？

如果我的这种说法正确，那么这里按照课文语境应该理解成过去的经常性的习惯（就是对应的一般现在时的过去时），

但是如果有人理解成做过某事（动作结束）= collected 动作结束，怎么办呢？这时，是否需要使用had collected 来明确吗？

我的疑惑其实是一般过去时如何判断是表示结束的动作，还是经常性的过去行为？怎么区分？

（例如It rained - 是下雨动作结束？还是表示过去经常下雨？）

2）后面的was growing为何用进行时，而没有使用过去时grew？用过去进行时意义何在？老师最好在此，对比was growing 和 grew 的含义分析，以便让学生理解。