In some contexts, "quelles" translates as "what". For example in English the query "What kinds of girls eat chocolate? Hungry ones? Sad ones? Fat ones? Thin ones? Happy ones?" might be phrased as "What girls eat chocolate?" and a good translation of this would be "Quelles filles mangent le chocolat?"
From what I understand, the wrongly heard homophones are accepted by Duo since you'd never know which is which because there is no context (although they still give the correct translation). In the colors lesson, for example, I kept typing "J'aime le verre" (I like the glass) instead of "J'aime le vert" (I like the green), but it was still marked as correct (although the translation was ALWAYS "I like the green"). Curious as to why this is so, I did my research and found out they were homophones. In the same manner, "quelle fille" and "quelles filles" have no difference in pronunciation, which is (I believe) why your answer was accepted despite the fact that the translation was for another sentence. However, if the plural and singular nouns (or articles) have different sounds, or the sentence has differently sounding verbs for the sing and pl nouns, they will mark you wrong, so watch out!
For the record, verte is not a homophone for verre, as the you pronounce the T in verTe.
Also, to talk about the colour green as a noun, you would use the masculine form, vert, which is a homophone for verre. (Although, somewhat confusingly, the French for "the colour green" is "la couleur verte", as couleur is feminine!)
Oh, I'm sorry! >.< It seems I've become too indulgent with my e's yet again (a horrible habit I've yet to get rid of). Thank you for pointing it out. I have edited my original post to the correct word. Thank you also for explaining about the use of the color green as a noun! Do the other colors also follow the same rule, I wonder?
Quelle, quelles, quel, quels = placed directly before the noun they modify or used in a sentence like this one: "Quelles sont tes filles ?" = "Which are your daughters?"
- Quelles filles mangent le chocolat ? = Which girls eat the chocolate?
- Quelle fille mange le chocolat ? = Which girl eats the chocolate?
- Laquelle des filles mange le chocolat ? = Which one of the girls eats the chocolate?
- Lesquelles des filles mangent le chocolat ? = Which of the girls eat the chocolate?
- Lesquelles de ces filles mangent le chocolat ? = Which of these girls eat the chocolate
To know more, read this: http://www.duolingo.com/#/comment/572361
An article is a type of determiner, which means a word that introduces and modifies a noun. Quelle is an "interrogative determiner." An article is another type of determiner. You don't need more than one when introducing a noun. http://french.about.com/od/grammar/a/determiners.htm
No, "fils", meaning "son", sounds entirely different from "fille", meaning "girl" or "daughter". Unfortunately, the last time I heard her, our robot mispronounces "fils" quite egregiously, so this is likely to cause problems for new learners. "Fils" is properly pronounced FEESS (no "l" sound at all), while "fille" sounds like "FEEyuh" (that is, FEE with a very little bit of a "yuh" on the end).
http://translate.google.com/#fr/en/mon%20fils%3B%20ma%20fille (click on the "listen" icon to hear the difference)
There is another French word, "fil", which means "thread" and in that one you DO pronounce the "l" (FEEL), and in the plural, it looks just like "son" - "fils", but is still pronounced "FEEL". Our robot seems to have got her "fils" mixed up, which is a very annoying problem that DL has yet to fix.
If the difference between plural and singular cannot be heard in this sentence, then they should provide both versions in the English translation. In my case I typed singular "Quelle fille mange le chocolat?" and it got accepted with a translation with the plural "girls" in it. That's quite confusing...