Write an Equation for the Parabola with Vertex at the Origin

Multiple Choice

Write an equation for the parabola with vertex at the origin.
-Through $( 3 , - 6 )$ , opening downward

A) $x ^ { 2 } = - \frac { 3 } { 2 } y$
B) $x ^ { 2 } = - \frac { 2 } { 3 }$
C) $y = \frac { 2 } { 3 } x ^ { 2 }$
D) $x = - \frac { 2 } { 3 } y ^ { 2 }$