When the teacher arrived, some students (be) diligently working on their projects for hours.
When the teacher arrived, some students had been diligently working on their projects for hours.
I (be) to five countries in Europe.
I’ve been to five countries in Europe.
We (meet) in January 1975.
We met in January 1975.
When the teacher arrived, some students (finish / already) their assignments.
When the teacher arrived, some students had already finished their assignments.
I (not / see) her since January 2022.
I haven’t seen her since January 2022.
When the teacher arrived, some students (display) bad attitudes for quite some time.
When the teacher arrived, some students had been displaying bad attitudes for quite some time.
When the teacher arrived, some students (snapchat - VERB).
When the teacher arrived, some students were snapchatting.
The last time I (see) him was over a year ago.
The last time I saw him was over a year ago.
I (be) to five countries in Europe by 2001.
I’d been to five countries in Europe by 2001.
We (go) to America together in 2008.
We went to America together in 2008.
When the teacher arrived, the room (be) a complete mess.
When the teacher arrived, the room was a complete mess.
When the teacher arrived, some students (finish / still) their assignments.
When the teacher arrived, some students were still finishing their assignments.