Expressing obligation: must, mustn't, have to, don't have to Expressing obligation: must, mustn't, have to, don't have to
MUST, MUSTN’T, CAN, CAN’T, COULD, COULDN’T, SHOULD or SHOUL’T MUST, MUSTN’T, CAN, CAN’T, COULD, COULDN’T, SHOULD or SHOUL’T