🕵️ Grammar B1-25: Modals of deduction (present)

The twenty-fifth material of the Fleydo B1 grammar series turns the learner into a detective: every modal of deduction is a verdict resting on a piece of evidence. must says the facts allow exactly one answer — the lights are off, so they must be out; might, may and could say several answers are still alive; can’t says the evidence rules this one out — that can’t be Jess, she’s at the dentist. The teaching hangs on one scale with two sure ends and a maybe middle, and on the asymmetry that costs B1 marks every year: the opposite of must be is can’t be, while mustn’t stays in the rulebook giving orders. A four-question decision routine — find the evidence, count the explanations, keep the middle words while several survive, use can’t when a door shuts — is walked through three worked runs, one of them adding be + -ing for deductions about actions happening right now, such as she must be sleeping. Six evidence cards make the learner commit to a verdict before checking, a knock-at-the-door compare puts must be and can’t be side by side, and a note separates the weak no, might not, from the strong no, can’t. Practice is spread across four sets of eight, seven, eight and eight items — every stem carrying its own clue and every answer explaining its reason — plus ten pieces of evidence to sort by how many answers they allow, six real learner errors to repair and three traps led by mustn’t invading the deduction scale. A 130-word missing-cake mystery gives eight tappable verdicts, each pointing at the evidence it rests on. Teacher notes add a 45-minute sequence, the certainty-line board move with mustn’t exiled to a RULES box, a physical rescue drill, Cambridge B1 Preliminary relevance and a preview of past deduction at B2-7.