Form 5ac. Revision on grammar

For practicing:
https://www.learnenglishfeelgood.com/english-verbs-tobe1.html;
https://www.grammarbank.com/verb-to-be.html;
https://www.perfect-english-grammar.com/present-simple-exercise-11.html;
https://www.perfect-english-grammar.com/present-simple-exercise-14.html;
https://www.perfect-english-grammar.com/present-simple-exercise-15.html;
https://www.englishexercises.org/makeagame/viewgame.asp?id=2842;
https://www.englishgrammar.org/pronouns-exercise-beginner-level/;
https://www.englisch-hilfen.de/en/exercises/plural1/index.php;
https://www.englisch-hilfen.de/en/exercises/nouns_articles/plural2.htm;
https://www.englishexercises.org/makeagame/viewgame.asp?id=723.