On utilise les modaux de déduction pour exprimer notre degré de certitude sur une situation présente ou passée.

1. Déduction au Présent

Must (Certitude quasi-totale - 95%) : On est sûr que c’est vrai.
- He is driving a Ferrari. He must be rich. (Il doit être riche).
Might / May / Could (Possibilité - 50%) : On n’est pas sûr.
- She isn’t answering. She might be sleeping. (Elle dort peut-être).
Can’t (Certitude négative - 95%) : On est sûr que c’est impossible.
- He only left 2 minutes ago. He can’t be home yet. (Il ne peut pas déjà être chez lui).

2. Déduction au Passé

Structure : Modal + HAVE + Participe Passé.

Must have : You must have been happy when you won! (Tu as dû être heureux).
Might have : I can’t find my keys. I might have left them in the car. (Je les ai peut-être laissées…).
Can’t have : She can’t have seen me, I was hiding. (Elle n’a pas pu me voir).

Complète avec Must, Might ou Can’t (au présent ou au passé).

#1 He has three PhDs. He

be very intelligent.

#2 I'm not sure where he is. He

be at the gym.

#3 You just had lunch! You

be hungry already.

#4 She looks exactly like her mother. She

be her daughter.

#5 The lights are off. They

have gone out.

#6 I don't know why she's late. She

have missed her bus.

#7 He

have stolen the money. He was with me all day!

#8 Look at the sky! It

rain later.

#9 She's wearing a ring. She

be married.

#10 You

be serious! That's impossible!