Даю много баллов. Complete the dialogue with: must, mustn039;t,have to, don039;t

Даю много баллов. Complete the dialogue with: must, mustn't,have to, don't have to,don't need to ,might. Give reasons for your choices.
A:Hi,John.What are you doing here?
B:I want to sign up for an exercise class. My doctor says I 1)................... lose some weight.
A:You 2)................. lose a lot.You should try the aerobics class that I teach.
B:I know I 3)..................... do some exercise,but perhaps your aerobics class is too much for beginners like me.
A:You 4)..................... give up so easly ,John.Try one lesson .You 5)..................... carry on if you don't like it .
B:Mmm,I'm not sure.
A: You never know!You 6)................ enjoi it!