Which is the equation of an ellipse centered at the origin with vertices (8,0) and (-8,0) and a minor axis length of 8?

the standard form of an ellipse with horizontal major axis as in this problem is:
[tex] \frac{ x^{2} }{ a^{2} } + \frac{ y^{2} }{ b^{2} } =1[/tex] where 
"a" is greater than "b"

the major axis is length of 16 which means  a = 8 and the minor axis length is 8 which means b = 4

the equation then is:   Choice B