Answer:
A
Step-by-step explanation:
A function is any relation for which an input does <em>not</em> equal two different outputs. For instance, if a set contains (1, 1) and (1, 2), then the set is not a function. However, a set that contains (1,1) and (1,1) is a function because it's the same thing. In other words, the x-coordinate cannot repeat. If it does, it must equal to same thing.
For W, none of the x-coordinates are repeated. Thus, W is a function.
Similarly, for X, none of the x-coordinates are repeated either. X is a function.
Again, for Y, none of the x-coordinates are repeated. Y is a function.
Lastly, for Z, the same thing. None of the x-coordinates are repeated, so Z is a function.
Thus, all choices are a function. The answer is A.
