关于情态动词的题目A:How can I get thinner?B;Well,you______eat food wi

关于情态动词的题目
A:How can I get thinner?
B;Well,you______eat food with plebty of fibre that helps you digest better.(横线中填have to 还是 should还是ought to 我觉得有劝告的意思在里面,应该填should/ought to)
A;Does it mean I_______eat my favourite fired chicken any more?(横线填mustn't还是shouldn't?)
B;Not exactly,if you love fried chicken,you_____give it up(should还是needn't)You needn't worry too much;a little fried chicken_____do you good(can还是will)
到底如何判断?望高手指教!