Past perfect vs. past simple
Learners often confuse the past perfect with the past simple.
We use the past perfect tense to refer to events which happened at an earlier point in the past, compared with another past event. We use the past simple for an event which occurred generally in the past.
[latex]\color{limegreen}{\checkmark}[/latex] By the time I got there, he had left.
✗ By the time I got there, he left.
Complete the sentences using the correct form of the verb in brackets.