"Who put this book on the desk?"

Translation: Siapa yang menaruh buku ini di atas meja?

[kuyaC]

I wrote the same thing without "yang". Isn't that correct?

[WayangOrang]

'yang' cannot be left out here.

It's explained in one of the grammar topics in the forum.

..edit... :
this topic :

Apa, Siapa, Tips & Notes, Addendum.
https://forum.duolingo.com/comment/31279456

[Jake929031]

Really that doesn't make sense it would seem to work fine without yang.

Seaching google with yang is more common than without but without is still used. Guess it is just not official like much Indo.

[Rick392366]

Well, it looks like you don't understand that topic.

Have you read that topic ?

Maybe you should read it again.

Selamat belajar.

[Jake929031]

No I read it, I gather use of yang is the official way.

If you look at say Siapa mau vs Siapa yang mau, its 2vs10million uses. Quite a difference but without yang is used often enough that it is normal I think. I have certainly heard without yang many times.

I think the problem you run into trying to codify Indonesian is it is a relatively rapidly changing language. Given the conditions of Indonesia that is not surprising. I suggest you just move with the evolution and if possible adopt the more efficient use. Otherwise you will most likely end up with a dead language. It is a bit disappointing you made a new language and didn't adopt an existing one. But not surprising given your general state of mind. You do continue to adopt English, who knows you may all end up just speaking Chinese one day.