https://agendaweb.org/exercises/grammar/comparison/comparatives-1
http://s.mound.free.fr/skyblues67/comparing/trig&family1.htm
https://agendaweb.org/exercises/grammar/comparison/comparison-multiple-2
http://www.bbc.co.uk/worldservice/learningenglish/youmeus/quiznet/newquiz62.shtml
https://www.learnenglishfeelgood.com/english-comparative-adjectives1.html
http://www.eslkidsworld.com/Interactive%20games/comparatives%20and%20superlatives%20animals%20football%20quiz.html