Sentence Correction

I know this question may seem to be easy to you guys, but I think there would be somebody like me wants to know the answer:
I'm going to make dinner for Frank.
I'm making dinner for Judy.
I'll make dinner for Mary.
I make dinner for Ted.
I will be making dinner for Tony.
Who are you offering to make dinner for?
OA: Mary

Can anyone please further explain what the question is trying to say? And why the answer is that one?