PAST CONTINUOUS VS. PAST SIMPLE
http://www.perfect-english-grammar.com/past-simple-past-continuous-exercise-1.html
http://www.perfect-english-grammar.com/past-simple-past-continuous-exercise-2.html
https://elt.oup.com/student/project3rdedition/level5/unit1/grammar/exercise1?cc=us&selLanguage=en
https://elt.oup.com/student/project3rdedition/level5/unit1/grammar/exercise2?cc=ar&selLanguage=en
NEW ENGLISH FILE EXERCISES
https://elt.oup.com/student/englishfile/preint/a_grammar/file02/?cc=ar&selLanguage=en
SUBJECT-OBJECT QUESTIONS
Remember that subject questions are those WITHOUT auxiliares
object questions are those WITH auxiliaries
http://www.perfect-english-grammar.com/subject-questions-exercise-1.html