The last graph is the one that does not represent a function.
Which of the following does not represent a function?
To know if a graph represnts a function or not, we can try to use the vertical line test.
It says that if we can find a vertical line that intercepts the graph more than once, then the graph does not represent a function.
This is beacuse a function maps each input into a single output.
Using this test, we can see that the last graph does not represent a function (you can even see that the vertical axis intercepts two times the graph). so that is the correct option.