Right choice is (b) \(\frac{V_{org}}{V_w}\)
Easy explanation: Kbiphasic in terms of volumes is represented by
\(K_{biphasic} = K_w (\frac{1+αP_B}{1+αP_A})\),
Where Kw = equilibrium constant of water, PA and PB are partition coefficients of A and B respectively.
α is the ratio of the volumes of the organic (Vorg) and water (Vw) phases and is given by \(\frac{V_{org}}{V_w}\).
Kw = \(\frac{[B_w]}{[A_w]}\) ; \(K_{biphasic}=\frac{[B_t]}{[A_t]}\) ; and PB = \(\frac{[B_{org}]}{[B_w]}\).