Graph A is a function.
To determine if a graph is a function, it has to pass what we call the “Vertical Line Test.” In this test, the x-coordinate cannot repeat, and the graph cannot have multiple points on the same vertical line. An example of two points that would make a graph not a function would be (2, 5) and (2, 3). Because 2 repeats, the graph collectively isn’t a function. Graph A is the only graph that passes this test, so it would be a function.