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/Canluse your bathroom? 10) I must / can work harder, so I may be helpful.