PRACTICE ON LINE
http://www.xtec.cat/~ogodoy/sac/rephrasing/modalsex1.htm
http://www.cristinacabal.com/intermediate/modals2.htm
https://www.englishpractice.com/grammar/rewrite-modal-auxiliaries/
http://nacho.montorio.info/Real%20English/unit%204/rewritingmodals2.htm
http://www.e-grammar.org/modal-verbs-can-may-must/test3-exercise1/