Before we dive into past perfect tense. Let's quickly recap present perfect tense so that we may have clearer picture. Remember that "the present perfect tense is used to express actions or events that have occurred at some point in the past but are still relevant or have an effect in the present.".
The past perfect tense in English is used to describe an action or event that was …
1. she / finish / homework / before dinner
2. we / not arrive / by the time / concert / start
3. the plane / already take off / by the time / they / arrive
4. we / finish / dinner / by the time / guests / arrive
5. I / not sleep / much / before / exam / start
