a function is where there is only one output for every input. so when you plug in an x value, you should be getting only one y value.
it’s not the first one because you can see there are two points at (-1,0)
it’s not the second one because you can see there are two points at (0,0)
it’s not the fourth one because again there are two points at (-2,0) and (2,0)
it’s the third one because there is only one y value for every x value.
