14. 將Bessel equation x2yn + xy' + (k2x2 - v2)y = 0（其中v、k為常數）化成Sturm-Liouville之形式為，下列何者正確？ (A)p(x) = x2 (B)p(x) = x2/2 + x (C)p(x) = x (D)p(x) = x1/2