1-fanele-bo-‘You must go to school to lay a secure foundation for your future’ — Kufanele uye esikoleni ukuze uyobeka isisekelo esiqinile sekusasa lakho
2-ngenzeka‘The tree must have been blown over in the storm last night’ — Umuthi kungenzeka ukuthi uphephuke esiphephweni sayizolo ebusuku
We use mustn't when we want to tell someone not to do something. We don't use mustn't if the person has a choice. We say you don't have to instead.