Answer
$y^2 =4$ in 3D is the two parallel vertical planes $y=-2$ and $y=2$
Work Step by Step
$y^2=4$ has two solutions: $y=2$ and $y=-2$
Since $z$ and $x$ can be any real numbers, $y^2 =4$ in 3D is the the two parallel vertical planes $y=-2$ and $y=2$
