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