The graph of f(x) = x^2 was transformed to create a graph g(x) = f (x) - 6.
Which statement about the graphs is true?

A. The vertex of the graph of g is 6 units to the right of the vertex of the graph of f.
B. The vertex of the graph of g is 6 units above the vertex of the graph of f.
C. The vertex of the graph of g is 6 units below the vertex of the graph of f.
D. The vertex of the graph of g is 6 units to the left of the vertex of the graph of f.