Find the Standard-Form Equation of the Ellipse Centered at the Origin

Multiple Choice

Find the standard-form equation of the ellipse centered at the origin and satisfying the given conditions.
-An ellipse with length of major axis 18 and $y$ -intercepts $( 0 , \pm 5 )$

A) $\frac { x ^ { 2 } } { 81 } + \frac { y ^ { 2 } } { 25 } = 1$
B) $\frac { x ^ { 2 } } { 9 } + \frac { y ^ { 2 } } { 5 } = 1$
C) $\frac { x ^ { 2 } } { 25 } + \frac { y ^ { 2 } } { 81 } = 1$
D) $\frac { x ^ { 2 } } { 5 } + \frac { y ^ { 2 } } { 9 } = 1$