Lesson on the Past Perfect Continuous (I had been studying for hours)

In this lesson, Mark explains the past perfect continuous tense, which is used to describe actions that happened progressively in the past before another action. He provides examples and compares it with the past continuous tense, highlighting the differences in emphasis on duration versus interruption. The lesson includes the formula for constructing sentences, forming questions, and making negative statements. Mark concludes with a recap and a question for the audience.

In what context would you use the past perfect continuous tense?

What auxiliary verb is used in the past perfect continuous tense?