https://www.perfect-english-grammar.com/present-continuous-exercise-1.html
https://agendaweb.org/verbs/present-continuous/index.html
https://agendaweb.org/exercises/verbs/present-continuous-progressive/positive-negative-questions-write.htm
https://www.eslgamesplus.com/present-progressive-continuous-esl-grammar-fun-game-online/