Réponse :
a- at lunch time, josh doesn't have to go to the canteen ...
b- you must be 16 to have...
c- in josh's scool, you mustn't have to call the teachers....
d-josh must wear a uniform but he doesn't have to wear a hat
Explications :
must designe l'obligation
must not (musn't) designe linterdiction
not have to designe le fait que ce n'est pas obligé