https://www.britishcouncil.org.mx/blog/modal-verbs

https://englishlive.ef.com/es-mx/blog/laboratorio-de-gramatica/modal-verbs/

https://agendaweb.org/verbs/modals-exercises.html

https://www.english-grammar.at/online_exercises/modal-verbs/modal-verbs-index.htm

https://youtu.be/PDtUTAwMGDQ

https://youtu.be/hT5PWuuxaKM

https://agendaweb.org/verbs/conditional-verbs-exercises.html

https://www.englisch-hilfen.de/en/exercises/if_clauses/zero_conditional.htm

http://www.learnenglish-online.com/grammar/tests/zeroconditional.html

https://agendaweb.org/verbs/conditional-first-exercises.html

https://www.englishexercises.org/makeagame/viewgame.asp?id=3226

https://agendaweb.org/vocabulary/clothes-exercises.html

https://www.inglessencillo.com/pasado-simple

http://www.aprenderinglesfacil.es/2008/04/pasado-simple-simple-past-tense.html

http://www.agendaweb.org/verbs/past_simple-exercises.html

https://www.lewolang.com/gramatica-inglesa/4/personal-pronouns

https://www.aprendeinglessila.com/2018/03/object-pronouns-pronombres-objeto-en-ingles/

https://www.lewolang.com/gramatica-inglesa/35/possessive-adjectives

https://www.lewolang.com/gramatica-inglesa/69/possessive-pronouns

https://agendaweb.org/grammar/personal-pronouns-exercises.html

https://agendaweb.org/grammar/pronouns-objects.html

https://agendaweb.org/grammar/pronouns-mixed.html

https://agendaweb.org/grammar/possessive-pronouns-exercises.html

http://www.curso-ingles.com/aprender/cursos/nivel-intermedio/verb-tenses-past/used-to

http://www.englishexercises.org/makeagame/viewgame.asp?id=1230

https://agendaweb.org/verbs/to-be-used-to.html

https://www.englishclub.com/esl-games/grammar/jumbled-past-used-to-1.htm

http://www.perfect-english-grammar.com/used-to-exercise-1.html

 http://www.curso-ingles.com/aprender/cursos/nivel-intermedio/comparative-superlative/comparatives-and-superlatives

 https://www.youtube.com/watch?v=KdGbGhp6UwA 

https://agendaweb.org/grammar/comparison-superlative-exercises.html

http://anthonyhalderman.com/english/compsup.htm

http://www.englishexercises.org/makeagame/viewgame.asp?id=13691

https://www.eslgamesplus.com/comparatives-superlatives-wild-zoo-animals-vocabulary-grammar-interactive-monkey-fun-activity/

https://www.ego4u.com/en/cram-up/grammar/adjectives-adverbs/adjectives/exercises