"Julia is a very good girl."
Translation:जूलिया एक बहुत अच्छी लड़की है।
But this English sentence only includes "a" because it has to to be grammatically correct. It needs an article in the way Hindi doesn't. If you said, "Julia is one very good girl" it wouldn't be grammatical except in a particular informal style of speech.
Anyway, my point is that I had the same answer as the original poster, and I agree that it should not be marked incorrect.