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https://www.englishpage.com/verbpage/verbs13.htm
https://www.englishpage.com/verbpage/verbs14.htm
https://www.englishpage.com/verbpage/verbs15.htm
https://www.englishpage.com/verbpage/verbs16.htm
https://www.englishpage.com/verbpage/verbs17.htm
https://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-9553.php
https://elt.oup.com/student/solutions/upperint/grammar/grammar_02_022e?cc=ar&selLanguage=en
https://www.myenglishpages.com/site_php_files/grammar-exercise-past-perfect.php
https://www.englishpage.com/verbpage/verbs13.htm
https://www.e-grammar.org/past-perfect-simple-continuous/test1-exercise1/
https://www.perfect-english-grammar.com/past-perfect-continuous-past-simple-exercise-1.html