本文目录
过去完成进行时是英语语法中的一种时态，通常用来描述过去某一时刻之前已经开始并一直持续到过去另一时刻的动作或状态。在使用过去完成进行时时，我们需要注意一些关键词，以便更好地理解和运用这种时态。
以下是一些常见的过去完成进行时的关键词：
for 和 since
for 和 since 都可以用来表示过去的一段时间。for 通常用来表示一段具体的时间，例如：
- I had been studying English for three hours before I finally stopped.
- They had been waiting for the bus for half an hour before it arrived.
since 则通常用来表示一个具体的时间点，例如：
- She had been living in New York since 2010 before she moved to Los Angeles.
- He had been playing video games since noon before he realized how much time had passed.
all day / week / month 等
all day、all week、all month 等时间段的词语也可以用来表示过去完成进行时，例如：
- I had been working all day before I went to bed.
- They had been traveling all week before they arrived in Paris.
before
before 可以用来表示过去完成进行时的动作或状态在过去某一时刻之前已经开始了，例如：
- I had been practicing my speech for hours before I finally felt confident.
- They had been planning their trip for weeks before they finally booked their tickets.
以上是一些常用的过去完成进行时的关键词，运用这些关键词可以帮助我们更好地理解和使用这种时态，提高英语表达的准确性和流利度。
