Answer:
A. Sandy :- 1 - must
Lucky :- 2- must 3- mustn't
Sandy :- 4 - must 5- don't 6 - have to
Lucky :- 7 - mustn't.
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B. 1 - shouldn't
2- should
3- shouldn't
4 - should
5 - shouldn't
6 - should
7 - should
8 - should
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C. 1 - My sister must tidy her bedroom now.
2 - You mustn't shout in the class.
3 - My parents must do sport every day.
4 - They mustn't wake the baby.
5 - We mustn't walk on the glass.
6 - He must buy some fruits.
7 - You must go to the hospital if you have a cold.
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I hope this is helpful to you!!