Write an Equation for a Cross Section of the Parabolic $x ^ { 2 } = 9 y$

Multiple Choice

Write an equation for a cross section of the parabolic ear (used to hear sounds from a distance) shown in the picture. ​ d = 2.25 inches

A) $x ^ { 2 } = 9 y$
B) ​ $y ^ { 2 } = \frac { 1 } { 9 } x$
C) ​ $x ^ { 2 } = 2.25 y$
D) ​ $y ^ { 2 } = 2.25 x$
E) $y ^ { 2 } = 9 x$