Answer:
The last one, D it is not a function because the domain (x) does not repeat.
Explanation:
To find whether it is a function or not ALL YOU NEED TO DO is check if the domain (x) repeats, it also includes negative numbers like if the domain is
-2, 3, 5, 2 it will be a function because none of these numbers repeat. Yes the number "-2, and 2" repeat BUT one is negative and one is positive, therefore it is a function because they are different numbers when they are negative and positives.
Also just wanted to mention if the (y) repeats it does not matter. It can repeat even a million times, but if the domain numbers (x) do not repeat, therefore it is a function.