Doing a vertical line test is like drawing a vertical line anywhere in the graph. If the vertical line hits only one point in the graph, the graph is considered a function. Otherwise, it is not.
Let's check the graph that we have here.
The red line is the vertical line drawn to test whether the graph (in green) is a function. As you can see, the vertical line only hit the graph at one point (in blue). Wherever you draw the vertical line in this graph, it will only hit at just one point.
Therefore, this graph is a graph of a function. The answer is Yes.