Ответ:
Краткое пояснение: Используем must/have to для выражения долженствования, mustn't для запрета, don't have to, чтобы сказать, что что-то не обязательно.
- have to and must to talk about rules and things that are necessary.
- We use mustn't when something isn't allowed by a rule.
- We use don't have to when something isn't necessary. We use didn't have to when something wasn't necessary in the past.
- We use had to for rules in the past.
Ответ: