"Saya memakan apel itu."
Terjemahan:I eat the apple.
It should be 'i eat that apple' Bcause u add 'itu' on the last sentence.. If u want to make 'i eat the apple', in bahasa it will be 'saya makan apel' That's it
"I eat that apple" should also be accepted.
I think the Duolingo team uses "itu" to make it consistent with other sentences where they translate "the" into "itu".