Answer
$A.$
Work Step by Step
Axis of symmetry is parallel to the $x$ -axis, opens right.
According to Table 2,
Equation: $(y-k)^{2}=4a(x-h)\quad $
Vertex:$\quad (h,k)$
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$(h,k)=(0,0)$,
so look for $y^{2}=4ax\quad $.... choice $A.$