Let's see if we can solve this problem. In this problem, we have 3 different graphs, and we're asked to determine below which of the graphs are functions, and we can select all that apply. Whenever you want to figure out whether or not a graph is a function, you can use the vertical line test. If you can draw a vertical line somewhere on the graph that crosses through more than one point, it is not a function. However, if the vertical line you draw only can cross through one point at most anywhere you draw it, it is a function. So let's see if we can figure this out.
Now for this first graph, we'll try the vertical line test. If I draw a vertical line here, we only cross through one point. If I try a vertical line over here, we only cross through one point. If I try a vertical line through the center or close to the center, we only cross through one point. And it turns out even though this graph expands in both directions, anywhere you would draw a vertical line would only ever cross through one point. So we can see that this first graph, graph A, is an example of a function.
But let's try graph B over here, and I'll go ahead and draw a vertical line. Notice the vertical line we drew crosses through more than one point. Since we see that we can draw a vertical line somewhere that crosses through more than one point, that means this is not an example of a function.
But now let's try the vertical line test on this graph over here. Well, if I draw a vertical line there, we only cross through one point. If I draw a vertical line here, only cross through one point. And anywhere I would draw this vertical line would only ever cross through one point. So we would say that graph C is an example of a function.
So, to list all of the graphs that are functions, we would say graph A and graph C are functions. That's the answer to this problem.