https://agendaweb.org/verbs/present_simple-exercises.html
https://agendaweb.org/verbs/present-simple-negative.html
https://agendaweb.org/verbs/present-simple-interrogative-exercises.html
https://agendaweb.org/verbs/present-simple.html
https://www.perfect-english-grammar.com/simple-present-exercises.html