5th LEVEL. GRAMMAR UNIT 3 EOI REUS OVERVIEW: MODALS OF SPECULATION1) If we are CERTAIN about something we use the following modal verbs ofspeculation: MUST, CAN’T or COULDN’T + INFINITIVE Used to talk about the present: That man over there must be the doctor. He’s wearing a white coat. He can’t /couldn’t be a doctor. He isn’t wearing a white coat. (NOT MUSN’T) CAN’T/COULDN’T + HAVE + PAST PARTICIPLE. MUST + HAVE + PAST PARTICIPLE. To talk about the past: It must have taken you a lot of effort to do this writing (a good writing). It can’t / couldn’t have taken you…. (a writing full of mistakes).2) If we are NOT CERTAIN about something but we think it is POSSIBLE . To talk about the present: MAY /MIGHT /COULD = maybe, perhaps. The shops may / might / could be open today. In the negative MAY / MIGHT + NOT The shops may / might not be open today. BUT!! COULD + NOT can’t be used in this way, it has a very different meaning: impossibility He was too far away so he couldn’t have seen you. To talk about the past: MAY /MIGHT /COULD + HAVE + PAST PARTICIPLE. I think I might have forgotten my book in the car. To talk about the future: It might / may / could rain.