Choose the modals which express prohibition. Can't; Don't have to; Don't need to; Mustn't; Needn't to; Oughtn't to; Shouldn't. Choose the modals which express the absence of necessity. Can't; Don't have to; Don't need to; Mustn't Needn't to; Oughtn't to; Shouldn't. Choose the modals which express warning or advice not to do something. Can't; Don't have to; Don't need to; Mustn't; Needn't to; Oughtn't to; Shouldn't.