3 предложения с Must (про зоопарк)
3 предложения с Mustn't (про зоопарк)

You mustn`t feed animals at the zoo.  
You mustn’t open the cages at the zoo.
You mustn’t touch the animals at the zoo.  

You must buy a ticket at the zoo.
You must keep the rules at the zoo.
You must look after animals at the zoo.