4B Modals of obligation: must, have to, should. Key

ex a 2 mustn't / 3 don't have to / 4 must / have to / 5 should / 6 doesn't have to / 7 mustn't / 8 mustn't / 9 should

ex b 2 mustn't / 3 don't have to / 4 have to / must / 5 don't have to / 6 must / have to / 7 mustn't / 8 have to / must