English: expressing obligation and prohibition
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Ability: can, be able to, could. Possibility: could, may, might. Positive deduction: must. Negative deduction: can’t. Obligation: must/ have to. Necessity: need to. Positive recommendation: should/ ought to. Prohibition: Mustn’t, can’t. No obligation: don’t have to, don’t need to, needn’t. Negative Recommendation: shouldn’t, oughtn’t to. Permission: can, could, may
Modal perfects. Positive deduction past event: must have + 3, Negative..: can’t have+ 3, possibility: may have/ might have + 3, could have + 3. Criticar: should have/ ought to have + 3.