Question

Which of the equations below could be the equation of this parabola?

Answer 1

Parabolas like $y=ax^2$ have the y-axis as their symmetry axis, so options B and D are surely wrong.

Moreover, parabolas like $x=ay^2$ have the x-axis as their symmetry axis. If $a>0$ the parabola is concave rightwards, if $a$ the parabola is concave leftwards.

Since your parabola is concave leftwards, the only feasible option is $x=-2y^2$