Why can't I answer with 'Die Frau isst Orangen' as well as 'Eine Frau isst Orangen'?
It says the other answer is Eine Frau isst Apfelsinen. for A woman eats oranges
What's your question? "Apfelsine" is another word for "Orange".
is there a specific time to use one or the other?
It's more of a regional thing. "Apfelsine" is more or less only used in northern and central Germany.
Why not Eine Dame instead of Eine Frau?
"Eine Dame" = "a lady"
What's wrong with "essen" in this case?