B2 · grammar

Modals of Deduction Exercises (B2) — Free

Modals of deduction: must, can't and might for present and past

Modals of deduction show how sure we are about something, based on evidence. Use must when you are almost sure something is true (The lights are on, so she must be at home), can't when you are almost sure it is not true (He can't be hungry; he's just eaten), and might, may or could when it's only possible (He might be at the gym, I'm not sure). For the past, add have + past participle: It must have rained in the night; She can't have seen me; They might have missed the bus. Couldn't can replace can't, especially in the past (She couldn't have seen me). A common mistake is using mustn't for a negative deduction: mustn't means 'it's not allowed', so say 'It can't be true', not 'It mustn't be true'. Read the context carefully: the evidence tells you how certain the speaker is.