Answer
In the graph by vertical line test, $y$ is not a function of $x$.
Work Step by Step
According to the vertical line test, if there is any intersection by any vertical line on a graph at more than one point (that is, for one value of x, there is more than 1 value of y), then the graph cannot be defined as y as a function of x.
In the graph, for one value of x, there is more than 1 value of y. Thus the graph does not pass the vertical line test. Therefore, $y$ is not a function of $x$.
Hence, $y$ is not a function of $x$.
