Fill in the blanks with: must or mustn't

Help me!!!!!!!!
Fill in the blanks with: must or mustn't
1) The traffic lights are red.You..........stop
2)There is an intersection ahead.We.......go fast
3)The traffic lights are yellow. You......slow down
4) The cars go very fast.We ........be careful
5)This sign says "Stop". We ..........go straight on
6) Our roads are dangerous places.We........have discipline
7)You........... drive your car carefully