Objective: How can I save my milk if I am going to be leaving town for a bit?

Which of the following solutions is more sound in terms of naive physics reasoning?

Possible answers: a). Freeze the milk, but make sure the jug is not more than 5/4 full at most. Then just let the milk thaw when you get back.. b). Freeze the milk, but make sure the jug is not more than 3/4 full at most. Then just let the milk thaw when you get back..
b).