Graph the equation. identify the vertex and the axis of symmetry.
y=-3x^2-6

select one:
a. vertex: (0, 6)
axis of symmetry: x = 0

b. vertex: (6,0)
axis of symmetry: x = 6

c. vertex: (0, -6)axis of symmetry: x = 0
d. vertex: (-6, 0)
axis of symmetry: x = -6