Write an Equation for the Parabola $x ^ { 2 } = 4 y$

Write an equation for the parabola.
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A) $x ^ { 2 } = 4 y$
B) $x ^ { 2 } = - 4 y$
C) $y ^ { 2 } = 4 x$
D) $y ^ { 2 } = - 4 x$