Совсем уже запутались в этим . fill in the gaps with mustn't or don't\doesn't have to. 1 you drink alcohol then you drive. 2 the windiws aren't very dirty. you clean them. 3 you smoke in bed. 4 he has enough food at home. he go shopping. 5 you walk on the grass here. 6 we've got a lot of time. we hurry. 7 you drive fast; there is a speed limit here. 8 you play football inside the house. go outside.

You mustn't drink alcohol when you drive.
The windows aren't very dirty. You don't need to clean them. 
You mustn't smoke in bed. 
He has enough food at home. He doesn't need to go shopping.
You mustn't walk on the grass here.
We've got a lot of time. We don't have to hurry.
You mustn't drive fast; there is a speed limit here.
You have to play football inside the house. Go outside.