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Electronic Resources:http://busyteacher.org/7763- 10 - teacher-tested-tricks-to-teach-modal-verbs.html
.https://learnenglish.britishcouncil.org/en/english-grammar/verbs/modal-verbs/certain-probable-
or-possible
http://usefulenglish.ru/grammar/modal-verbs-exercise-five
http://usefulenglish.ru/grammar/modal-verbs-exercise-six
http://www.teach-this.com/resources/grammar/modal-verbs-necessity