Which expression is used to say goodbye to someone in the evening? a. au revoir! à bientôt. b. au revoir! à plus tard. c. au revoir! bonne soirée. d. au revoir! à tout à l’heure.

It depends : )
if the narrator participates in the story (it’s a character of the story) then yes.
but if the narrator does’nt participate in the story (the narrator does not have a character) then no.