George visits us __________________ Christmas every year.
At | We use the preposition at when referring to special days or festivals like Christmas, Easter, etc. - so at Christmas is correct here since it's a specific
. I always get flowers ______________ my birthday.
On | We use the preposition on with specific dates and special days like birthdays, holidays, and weekends - that's why 'on my birthday' is correct.
Children go to school _________________weekdays
On | We use on when talking about specific days, including weekdays - just like we say 'on Monday' or 'on Saturday', we say 'on weekdays