Why do they not teach 고모 too? Or is that distinction archaic?
I don't know. But I'm familiar with both terms so it's okay. Have you heard the term 고모부?
이모와 이모부, 숙모와 숙부, 고모와 고모부, 백부와 백모
고모와 고모부, should also be accepted as answers. It really depends on which side of the family (maternal or paternal) you are talking to.
i think this should use 이모와 이모부, 숙모와 삼촌, or 고모와 삼촌 instead of mixing 이모 and 삼촌