Sure! Here are the completed sentences using the correct forms of "have to," "don't have to," "must," "must not," and "can't":
1 A Do teachers in your country have to look stylish?
B Not very stylish. They have to wear formal clothes, but they look neat.
2 A Do American taxi drivers have to know law?
B No. We have to work twelve hours a day, but we don't have to work every day.
3 A Do you have to do the cooking, but you must not help the children to eat.
4 B Does your husband have to travel abroad for his job?
A Yes, he must speak foreign languages.