The eccentricity of hyperbola $4x^2 - 9y^2 = 2ax + b^2$ is :

Question

( A ) $\frac{\sqrt{13}}{2}$
( B ) $\frac{a}{b}$
( C ) $\frac{\sqrt{b}}{a}$
( D ) $\frac{\sqrt{13}}{3}$