The general solution of the differential equation $x^2y^{\prime\prime}+ xy^\prime+(9 x^2-36)y=0$ is?

A. $c_1J_{-3}(6 x)+c_2Y_{3}(6 x)$

B. $c_1J_{-6}(3 x)+c_2J_{6}(3 x)$

C. $c_1J_{6}(3 x)+c_2Y_{6}(3 x)$

D. $c_1J_{3}(6 x)+c_2Y_{3}(6 x)$