modals expressing probability http://speakspeak.com/english-grammar-exercises/intermediate/modal-verbs-for-past-probability-must-have-cant-have-couldnt-have-may-have http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/410-modals-of-possibility-and-probability-for-past-situations1.htm https://sandymillin.wordpress.com/2011/10/18/key-word-transformations-with-modals-of-speculationdeduction/ B2 First Use of English Part One speculating practice B2 First Use of English Part Two speculating practice