"You eat oranges."
Translation:Sen portakal yersin.
Why not accept portakallar as well, since the question stem asks in English for the plural, "oranges"
This question has been tackled many times on other sentences too. You can find them by searching "plural accusative", I think. In short; Indefinite plurals sound plain ugly in Turkish. Singular is fine. Or just say "birçok" (many) "birkaç" (some), if you really want to emphasize the number.