Give the correct tense of the verbs in brackets.5.2
had done
to keep
(do) a lot of research, he started writing his report. X
7. It's necessary for us (keep) our environment clean. solo.
8. By the time I came back last night, every one
9. English is not easy
(go) to bed. v
(learn)
10. When I arrived at the movie theater, the movie
6. After he
(already/start