VOA慢速英语:The Perfect Progressive Tenses

短语讲解：

1. Perfect progressive sentences focus on the completion of an action that is, was or will be in progress.

focus on 致力于; 使聚焦于
例句：They must focus on improving the quality of the products.
他们必须注重提高产品质量。

2. Think about this sentence in the past perfect progressive:

think about 考虑…; 捉摸…
例句：Even now when I think about it I feel pain in my heart.
就是现在想起来我心里都感到难受。

3. In all of these sentences, the emphasis is on how the finished activity relates to the present.

relate to 涉及; 同…有…关系; 与…协调
例句：How do these relate to the product being designed?
这些经历同将要设计的产品有什么关系？

4. Sometimes we use it to refer to recently completed actions.

refer to 参考; 指的是; 涉及; 适用于
例句：Writers often refer to a dictionary.
作家时常参考字典。

5. For example, “The doctor will have been working for 24 hours by the time his shift is finished.”

work with 与…在一起干; 从事…工作
例句：For the sake of convenience we shall work with the space.
为了方便起见，我们将利用空间。