Chapter 10 - Analytic Geometry - 10.2 The Parabola - 10.2 Assess Your Understanding - Page 646: 9

c)

Its axis of symmetry is parallel to the $y$-axis, hence it can only be c) or d) and it only takes values $y\gt0$, hence it is c). (because the left side of the equation is non-negative, so the right side must be non-negative too.)