Answer:
X
Step-by-step explanation:
For a relationship to be a function, every input has exactly one output, so for every x value there is only one value.
If you look at answer's w and z for x=1 there is two y values, therefore they are not functions, letter Y is tricky. Even though every x value has only one y value, If you were to extend the graph x=0 would have more than one y values.
That leaves X. If you extend the graph of X every x value will only have one y value so it is a function
