Advanced Modal Verbs: Deduction & Speculation

**Present deduction:** - **must** = almost certain: He **must be** at the office. (I'm 95% sure) - **can't / couldn't** = impossible: She **can't be** sick — I just saw her! - **may / might / could** = possible: He **might be** stuck in traffic. **Past deduction:** - **must have** + pp: She **must have forgotten** the meeting. - **can't / couldn't have** + pp: He **can't have finished** so quickly! - **may / might / could have** + pp: They **might have left** already. **Should have** (expectation/criticism): - They **should have arrived** by now. (expectation) - You **should have studied** harder. (criticism) **Needn't have** vs **didn't need to:** - I **needn't have bought** a ticket. (I bought one, but it wasn't necessary) - I **didn't need to buy** a ticket. (I didn't buy one — it wasn't necessary) **Would have** (hypothetical past): - I **would have gone** to the concert, but it was sold out.