Let P and Q are points on the parabola y²=4ax with vertex O, such that OP is perpendicular to OQ and have lengths r₁ and r₂ respectively, then the value of (r₁⁴/³r₂⁴/³) / (r₁²/³r₂²/³) is :
A. 16a²
B. a²
C. 4a
D. None of these