Answer:
1 : 3
There are 3 cats, and 9 fish, but for some reason there isn't any choice for this.
The reason its 1:3 is because the answer is simplified. Its simplified down by 1/3.
So 1/3 of 3 is 1, meaning the cats = 3 or 1.
The fish is 1/3 of its original value which is 3. You can check by dividing 9 by 3.
P.S
Have an Amazing Day and Good Luck!
-Faker/Tosrel