Why "om natten" and not "i natten" given that the prior question gave "han arbejder i hverdagene" as the correct answer and not "om hverdagene"? I understand that repeated events in time requie the use of om and not i, but this rule seems inconsistent with saying "arbejder i hverdagene"?
Yes, that would convey the same meaning. It's shorter to say "at night" though. :)
Had "at the night" and the system wanted " IN the night"