1. It’s possible that they don’t live here any longer. a They mightn’t live here any longer.
2. It isn’t possible that they are twins. b They can’t be twins.
3. It could be that they are not married. a They mightn’t be married.
4. It isn’t possible that there is some milk in the fridge. a There can’t be any milk left.
5. I think I saw her go out. a She mightn’t be at home.