OTEAT Corpus C Task IV.Rewrite the sentences using must, mustn't need.has to ,don't have to 1.It's a good idea to eat a healthy diet. 2.It isn't necessary for children to buy a ticket. 3.It's our duty to look after our health. to do her exercise. 4.It's necessary for Assel Ita pgainst the rules to play football here.​