"Cats drink water."

Translation: Kucing minum air.

[alex.sunch]

Why not "kucing-kucing"?

[WayangOrang]

Why not "kucing-kucing"?

Should also be okay.
It's not really necessary to reduplicate when you talk about something in general (like in this sentence).

Same as :
Burung terbang ==> Birds fly.
Kucing tidak bisa terbang ==> Cats cannot fly.

No need to reduplicate when talking about something in general.
Plural is implied.

[Jake929031]

Duolingo is not clear on this but thanks. I have seen indos though use nondupicative specific plural uses.

[Away54]

Kucing-kucing minum air is accepted as a correct answer (September 23, 2020).

[Humairalee]

I thought was kucing itu minum air.

[Supriya131]

I think your sentence would translate to: That cat drinks water.