Which one means the same as the sentence given, (a) or

Which one means the same as the sentence given, (a) or (b)? (5 points)
1. Its possible that they dont live here any longer.
a They mightnt live here any longer. b They cant live here any longer.
2. It isnt possible that they are twins.
a They mightnt be twins. b They cant be twins.
3. It could be that they are not married.
a They mightnt be married. b They cant be married.
4. It isnt possible that there is some milk in the fridge.
a There cant be any milk left. b There mightnt be any milk left.
5. I think I saw her go out.
a She mightnt be at home. b She cant be at home.