Nouns
1. https://www.english-4u.de/en/grammar-exercises/irregular-plural.htm 2. https://www.english-4u.de/en/grammar-quizzes/singular-plural.htm 3.https://www.english-4u.de/en/grammar-exercises/one-ones.htm 4.https://www.englishexercises.org/makeagame/viewgame.asp?id=723 5.https://onlinetestpad.com/ru/test/629102-plural-form-of-noun 6. https://lim-english.com/tests/test-na-mnozhestvennoe-chislo-sushchestvitelnyh/