Answer with Explanation:
Following are the correct answers:
1. You mustn't touch those animals. They're dangerous.
Reason: As the animals might harm it is important that the person doesn't touch them. Hence mustn't is used.
2. We have to take the bus to school. It's too far to walk.
Reason: As the distance is very large. The author says that they should take the base. Hence, have to is used.
3. The concert is free. You don't have to pay.
Reason: The author implies that the concert is free hence no fees is needed. Thus don't have to is used.
4. It's late. I have to go now.
Reason: Author says that he has to go because it is getting late. Hence have to is used.
5. You mustn't leave the door open - the cats will come in.
Reason: Writer is warning to not open the door. Therefore, mustn't is used.
6. You don't have to come if you don't want to. I can go on my own.
Reason: Author tells his/her friend to not come if they don't want to. Hence, don't have to is used.
7. In Britain you have to drive on the left.
Reason: Author informs about left side driving in Britain. Hence, have to is used.
8. You don't have to be very tall to play football.
Reason: Writer suggests that tall height is not necessary to play football. Thus, don't have to is used.