Choose the right meaning of the sentences below. They must be exhausted. I'm sure they're exhausted. I'm sure they aren't exhausted. I'm not sure if they're exhausted or not. They may be exhausted. I'm sure they're exhausted. I'm sure they aren't exhausted. I'm not sure if they're exhausted or not. They can't be exhausted. I'm sure they're exhausted. I'm sure they aren't exhausted. I'm not sure if they're exhausted or not.