Answer:
x
Explanation:
To figure out if a graph shows a function, do the vertical line test.
Draw a vertical line on an x-coordinate, and if the x-coordinate has more than 1 y-coordinate, then it is not a function.
The definition of a function is for every input, there is only one output. If an x-coordinate has more than one y-coordinate, that option can be crossed out.
w : has every x coordinate has two y-coordinates, does not work.
x : every x coordinate has one y-coordinate, works.
y : x-coordinate '3' has multiple y-coordinates, does not work.
z : every x-coordinate drawn 2 y-coordinates, does not work.
x is the only function.