Answer: Top-Left straight line
Explanation:
A function on a graph is a line that does not overlap itself where two coordinates on the x-axis would be the same. All of the graphs except the top left one, are curved to where there would be two of the same coordinates for x. Also, a function is where each input (x) has only one output (y). Since the x coordinate is listed twice with DIFFERENT outputs, it cannot be a function.