## Precalculus (6th Edition)

The graph in Option C does not represent a function. The graph's equation is $x=y^2$.
The graph in Option C is not a function since it fails the vertical line test because most vertical lines that will pass through the graph will cross the graph at two points. From page 254 and 255 of this textbook, the equation of the graph in Option C is $x=y^2$.