To make deduction we can use different modals such as : Must, Might, May, Could and Can’t.

• We use ‘must’ when we are sure that something is true because of evidence. (eg. She must go shopping here because I often see her car in the car park.)

• We use ‘might’, ‘may’ or ‘could’ when we think that something is possible but we are uncertain. (eg. Dinner is supposed to be at 7 o’clock but it might be late if the oven doesn’t work.)

• We use can’t when we think that something isn’t possible / true. (eg. It can’t be Monday tomorrow ! It’s only Saturday.)

To form a sentence using must, might, may, could or can’t, the verb following the modal is always an infinitive verb.