It is probably the case that Brian is gray. It is unlikely that Mary went to the garden. It is improbable that John took the apple.
It is probably not the case that either John took the apple, or Mary went to the garden.
It is probably not the case that either John took the apple, or Mary went to the garden.
It is almost certain that either John took the apple, or Mary went to the garden.
Either John took the apple, or Mary went to the garden.