The graph of f(x)=x^2 was transformed to create the graph of g(x)=f(x)-4. Which statement about the graph is true? a) the graph of g is a reflection of the graph of f across the x-axis. b) the vertex of the graph of g is 4 units below the vertex of the graph of f. c) the graph of g is a reflection of the graph of f across the y-axis. d) the y-intercept of the graph of g is 4 units above the y-intercept of the graph of f