the voice says it wrong - don't know if that can be fixed. It is not pee-o, it is pjo.
Υλικό can also be translated as "ingredient", even if in this particular course it would sound weird ;o)
In addition to what Dimitra, with whom I agree, has said, is the meaning of "ingredient" as being a part of a whole while "material" can be an individual item.
See these links:
Well, it would indeed sound a bit weird, but I guess it could be okay.
The drop down menu gives "stuff" as a translation for iliko, then the program marks it wrong if you use it.
Sorry about that I've removed it. The secret of the drop down menu is that the word/words at the top are the ones used in the sentence you are doing. So, it's always best to choose the first hint.
I said "stuff" and was marked wrong…surprised but maybe I should stop thinking that this word means "stuff"?
Yes. Υλικό is actually not translated to stuff, at all.:P
Δεν είναι φυσική ομιλήτρια (για την ακρίβεια, δεν είναι καν ομιλήτρια), είναι ένα πρόγραμμα text-to-speech του duolingo. Γι αυτό μερικές λέξεις ακούγονται περίεργες. :S