过去完成式的形式如下：
had + past participle
过去完成式是不能单独用的。我们用的时候，必须有另一个事件。也就是说，假如我们有两件事 A 和 B，两件事都发生在过去，但 A 发生在 B 以前，A 应该用过去完成式，B 则用过去式。以下是几个例子：
（1） 他到台湾以前，曾学过中文。
He had studied Chinese before he came to Taiwan.
（2） 他念大学以前，曾前工作过。
He had worked before he decided to go to college.
（3） 我写这篇有关爱尔兰的小说以前，曾去过爱尔兰。
I had been to Ireland before I wrote this book about Ireland's people.
（4） 我在上大学以前，已经学过微积分。
I had studied calculus before I got into college.
（5） 周一以前，已经下过雪了。
It had already snowed before Monday.
如果我们要强调较早发生事件的连续性，我们可以用过去完成进行式。占去完成进行式和现在进行式惟一不同的地方是 verb to have 的地方一定要用had 。以下是一些过去完成进行式的例子：
1. I had been watching TV before you called me.
2. I had been working hard in a company for many years before I went to college.
3. He had been studying before he went to class.
4. He had been driving all day before he went to sleep.
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