It should be formal! (answer b).
The hint in the question is that the city major will attend the ceremony- this tells you that the ceremony will have a more representative, formal character, and will not be an internal celebration among people who know each other (this would make it informal or semi-formal).
True
Explanation:
I've worked in fastfood resturaunts, even though most had 4-5, you could easily feel like a puppet.