Compare the parent function f(x) = x^2 to the quadratic function f(x) = -2x^2 - 6.The 6 in the function does which of the following?
a. It makes the graph narrower than the parent function
b. It makes the graph wider than the parent function
c. It causes the graph to reflect across the x axis and open downward
d. It shifts the vertex of the graph vertically