"Does the child only eat breakfast?"
Translation:아이가 아침만 먹습니까?
That roughly translates to "does the child eat nothing but breakfast?" As far as I know, Duo prefers direct translations so that people would get used to the words and their direct meaning.
Tips and Notes say:
The particle 만 means only. The topic, subject, and object particles come after it.
So why does this not say 아침만을?
I believe the object particle can be dropped sometimes when the topic object is clear like in this case