Modal verbs
MUST / MUSTN'T
elt.oup.com/student/project3rdedition/level3/unit6/grammar/exercise2?cc=cz&selLanguage=cs
MUST / MUSTN'T / DON'T HAVE TO
elt.oup.com/student/project3rdedition/level3/unit6/grammar/exercise3?cc=cz&selLanguage=cs
SHOULD / SHOULDN'T
elt.oup.com/student/project3rdedition/level3/unit6/grammar/exercise1?cc=cz&selLanguage=cs