For a parabola, the vertex is the critical point, in other words, it is the maximum or the minimum of the function.
From the graph, we can see that the minimum (the minimum value of y) of the graph is 1. The vertex is the point (3,1).
Moreover, as we mentioned the vertex is always the minimum or the maximum, in this case, it is the minimum since the rest of the graph is 'above' that point.
The answer is option B. Vertex is a minimum point at (3,1)