Form 5ac. Verb 'to be'. Pronouns. Plurals

For practicing:
https://www.englisch-hilfen.de/en/exercises/tenses/be3.htm;
http://www.eclecticenglish.com/grammar/PresentSimpleToBe1A.html;
https://www.englishexercises.org/makeagame/viewgame.asp?id=2813;
https://www.myenglishpages.com/site_php_files/grammar-exercise-be-present.php;
https://www.englisch-hilfen.de/en/exercises/pronouns/personal_pronouns.htm;
https://www.englisch-hilfen.de/en/exercises/pronouns/mix.htm;
https://www.ego4u.com/en/cram-up/grammar/pronouns/exercises?02;
https://www.ego4u.com/en/cram-up/grammar/pronouns/exercises?03;
https://www.englisch-hilfen.de/en/exercises/nouns_articles/plural6.htm;
https://www.englisch-hilfen.de/en/exercises/nouns_articles/plural7.htm.
QUIZ:
https://www.proprofs.com/quiz-school/story.php?title=njy0mdk4j4vw;
https://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-80258.php;
https://www.proprofs.com/quiz-school/story.php?title=plural-noun-test.