1) The girl is rather young; she mustn't / can't be awake so late. 2) I think you mustn't / can't work harder. 3) Mustn't/ Can't you sit still?4) The car is his father's, we mustn't / can't take it. 5) Our teacher mustn't / can't be late for the classes either. 6) The water is rather hot, but I think you must / can drink it. 7) The soldiers must / can obey their officers. 8) You must / can pay for your lunch yourself if you want. 9) Must / Can I use your bathroom?10) I must / can work harder, sol may be helpful. 2 Fill in can/can't or must/mustn't.