No need to look at the first two. It’s the third choice, the graph. Easily to tell if a graph is a function, draw lines down the x axis. A single line should not touch the line on the graph more than once. Also called the vertical line test. Therefore the answer is the graph. The first one is definitely wrong because all the x are the same. So if you were to draw a line down the x axis at 0, that line would touch all points there.
