Translation:My mother's sisters do not eat chicken.
"Doesn't" is used in the singular form only. (example: 1:My mom doesn't eat chicken 2: She doesn't eat chicken 3: My friend doesn't eat chicken) Don't is used in the plural form or in the second person. (example: 1: Our priests don't pay taxes 2: My gay brothers don't use protection when fighting zombies 3: You don't have to report me, this is only educational!)
Short answer: Because that is not what it says...
"Le sorelle di mia madre non mangiano pollo." = "My mother's sisters..."
"Le mie zie non mangiano pollo." = "My aunts..."
[EN] Aunt \ Aunts = [IT] Zia \ Zie.
[EN] Auntie\Aunty = [IT] Zietta.
But, they could be either your father's or your mother's sisters, so...
(Or even the wives of your uncles.)
If you want to convey all of the information in the original Italian sentence, you'd have to say:
My mother's sisters \ My maternal aunts \ My aunts on my mother's side
Or something like that.
Duo's choice is neither longer nor more cumbersome than the alternatives.
Except that Mum (mom) and Mother
have two different words in Italian...
• [EN] Mother = [IT] Madre.
• [EN] Mum (Mom)⠀⠀= [IT] Mamma.
• [EN] Mummy (Mommy) = [IT] Mammina.
Also, you assumed that the fact that it's your mum is obvious,
but the Italian sentence does specifically say "My mother's".
If there is no other difference between your answer and Duolingo's,
(typo or something else)
then you should report it as "My answer should be accepted".
I find this comment of yours very peculiar, especially if you are a native speaker.
Italian is not a stressed-timed language: it is a syllable-timed language. The difference is rather important: it is English that "swallows" the non-stressed syllables.
Besides, the skills of hearing and pronouncing the vowels in a distinct manner is paramount to Italian, as it is the foundation on which its gender-based system is built.
Not sure if it is an issue with your system (PC, mobile..?) but I clearly hear le sorelle. Maybe your ear needs more training to recognize Italian sounds? If Italian is not your native language, your brain will try to narrow down the sounds to a familiar set, and that may lead to incorrect comprehension.
Practice, practice, practice is the key, the same way you would with a different grammar structure.
If your ear is fine, than your system is not.
I was not trying to be condescending: I was just saying that the audio sounds fine and I don't really understand on what basis you claim it is not since you are not a native speaker.
My "foundation" is that I am a native speaker.
The problem is audio problems are not consistent, that alone says it is not in the ear or system but the pronunciation. Foundation means facts not assertion. My friends and family are native speakers in English but if we got 5 together you would understand none of them while I would have to translate English to English all day and night.
If you encounter this again, you can report it as "My answer should be accepted". Here's a link to how:
It's not really a matter of good/bad English/Italian. It's more a matter of showing structures, constructs and grammar patterns.
When your get a grip on how to build a possessive sentence in Italian then you can swap words around and make real conversations rather than learning "useful" sentences and repeat them like in a phrase book.