Vezbanja -Modal verbs 
25 vezbanja must ,have to,don't have to
http://www.englishexercises.org/makeagame/viewgame.asp?id=2786#a 
30 vezbanja should,shouldn't
http://www.englishexercises.org/makeagame/viewgame.asp?id=2786#a
Mix
http://www.englishexercises.org/makeagame/viewgame.asp?id=3023
http://www.autoenglish.org/modalverbs/ModalsObligation.htm
http://www.tolearnenglish.com/english_lessons/must-mustn-t-or-don-t-have-to