Hey Mateusmatt! I think it might not be accepted because duolingo seems to prefer the closest translation. The "as" is not entirely necessary in Portuguese either, but since they included the "as", the word "the" is necessary because it changes the meaning, even if slightly:
"Ela corta as batatas" = She cuts the potatoes
"Ela corta batatas" = She cuts potatoes
See what I mean? Can I just say that every language I know have nailed the word "potato" as a perfect word for the food. It seems it is adorable everywhere. =)
I recently described the
é sound in ELA (é-lah) as the a in mattress (American English), and the
ê sound in ELE (ê-lee) as the "e" in begin. Or something like that.
This is how Brazilian Portuguese speakers easily tell them apart--by the sound of the first "e" in ele or ela (and not by the last letter, since it isn't clear in speech). I can't guarantee that the robot would say it correctly (especially in turtle speed), but I hope it helps! =]
That's a popular hypothesis, although there's no solid proof.