Time clauses
https://www.e-grammar.org/time-clauses/test1-exercise1/
https://www.focus.olsztyn.pl/en-english-grammar-time-clauses-exercises.html#.WRmfCTqkKM8
https://www.focus.olsztyn.pl/en-exercises-time-clauses-test-2.html#.WRmfCDqkKM8
https://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-13727.php