區分將來進行時與過去完成進行時

將來進行時
基本形式：will be doing；be going to be doing
用於描述未來將會發生並且會持續一段時間的動作。

過去完成進行時
基本形式：had been doing
用於描述一些開始於過去並結束於過去的動作。常與“for five minutes”“for two weeks”之類的短語搭配。

例句對比：
（1）
They had been talking about this problem for 2 hours before Tony arrived.在託尼到之前，他們已經談論這個問題談了2小時了。
They will be talking about this problem tomorrow.明天他們會談論這個問題。

（2）
She had been working at that company for three years when it went out of business.在公司停業之前她在這工作了3年了。
She will be working at that company in three years.3年內她都會在這個公司工作。

（3）
Mike wanted to sit down because he had been standing all day at work.麥克想要坐下，因爲他爲了工作站了一天了。
Mike will be standing all day tomorrow.麥克明天要站一天。

（4）
James had been teaching at the university for more than a year before he left for Asia.詹姆斯離開亞洲之前已經在這個大學教書超過一年了。
James will be teaching at the university.詹姆斯將會在這個大學任教。

（5）
I had been looking for it for days before I found it.我找這個東西找了好久了。
I will be looking for my book tonight.我今晚會找找我的書。

（6）
I had only been reading a few minutes when he came in.我剛看了幾分鐘他就進來了。
I will be reading books in 2 hours.兩小時內我都會在看書。

同樣是進行時，從以上例子想必能很清楚的分辨出兩個時態的區別。