https://www.aprenderinglesrapidoyfacil.com/2018/05/07/tercera-persona/
https://www.abaenglish.com/es/verbos-ingles/tercera-persona/
https://www.english-4u.de/en/grammar/present-simple.htm
http://www.ingles3016.com/2016/07/la-tercera-persona.html
https://www.ego4u.com/en/cram-up/tests/simple-present-1
https://agendaweb.org/verbs/present_simple-exercises.html
https://www.perfect-english-grammar.com/present-simple-exercise-7.html
https://www.englisch-hilfen.de/en/exercises/tenses/simple_present_mix.htm
https://www.learnenglish.de/grammar/adjectivetext.html
https://www.curso-ingles.com/aprender/cursos/nivel-basico/nouns/countable-and-uncountable-nouns
https://agendaweb.org/grammar/countable_uncountable-exercises.html