Let \( O (0,0) \) and \( A (0,1) \) be two fixed points. Then the locus of a point \( P \) such that the perimeter of \( \triangle A O P \) is 4, is :
(a) \( 8 x^{2}-9 y^{2}+9 y=18 \)
(b) \( 9 x^{2}-8 y^{2}+8 y=16 \)
(c) \( 9 x^{2}+8 y^{2}-8 y=16 \)
(d) \( 8 x^{2}+9 y^{2}-9 y=18 \)