"This river is your food source."

Translation: Sungai ini adalah sumber makanan kalian.

[DiegoJaviUnlam]

I have used the translation "Sungai ini sumber makananmu.", and it was rejected. I have made a report to be added.

Translations suggested by Duolingo:

Sungai ini adalah sumber makanan kalian.

Sungai ini sumber makanan kamu.

The translation "Sungai ini sumber makanan kalian." is already accepted.

I have not tried other variations, with "Anda" for "your", "ialah", "merupakan" for "is".

[Speedy12846]

A river does not give food.

[Jspharmando]

Adalah is "to be"
Adalah often used in Subject-To Be-Object
This river is your food source = Sungai ini adalah sumber makanan kalian/kamu/-mu

ialah (to be) = a link between two pieces of sentence which confirms the details or explanation of the first part.
adalah (to be) = identical to, has the same meaning as, belongs to a group or class