Bonjour,
Réponse :
a. In the 19th century a lot of poor children had to work all day.= •obligation
b. They weren't allowed to stay in bed late. = •interdiction
c. Lord Landley's son was allowed to play and have fun. = •permission
Les phrases évoquent l'interdiction, l'obligation et la permission au passé comme l'indique le complément de temps «in the 19th century » dans la phrase a.