"My newspapers are taken by my nephew."
Translation:Koran-koran saya diambil keponakan saya.
'oleh' can be omitted if the passive 'di-' verb is directly followed by the agent/actor.
'oleh' must be used if the passive 'di-' verb is followed something else than the agent/actor.
agent/actor = the one performing the action of the verb ==> 'keponakan saya'.
1) Koran-koran saya diambil (oleh) keponakan saya.
2) Koran-koran saya sudah diambil (oleh) keponakan saya tadi pagi.
3) Koran-koran saya sudah diambil tadi pagi oleh keponakan saya.
tadi pagi = this morning.
In sentence 1 and 2 , 'oleh' is optional.
In sentence 3, 'oleh' must be used.
Here is more info about the 'passive voice'
I was marked incorrect for not doubling the koran. I know saying koran twice is more accurate, but Duolingo often uses the singular form to mean plural, so why is it so important here all of a sudden?