Final answer:
The vertex of the parabola is the point where the graph attains its minimum point if it opens upward and the maximum point if it opens downward.
Step-by-step explanation:
The correct answer is a. Vertex. The vertex of a parabola is the point where the graph attains its minimum point if it opens upward and the maximum point if it opens downward. The vertex is also the point where the axis of symmetry intersects the graph. It is represented by the coordinates (h, k), where h is the x-coordinate and k is the y-coordinate of the vertex.