must ,have to 不得不 两者没有严格的区别,语气上有不同
must 主观
have to客观
mustn't 和 don't have to 意思不同
mustn't 不可以,不允许做某事
don't have to 不必要做某事
eg:you mustn't go out now.你现在不可以出去
you don't have to go out now.现在可以不用出去.