The expression relating molarity (M) and molality (m) or a solution is:

Question

(A) $m = \large\frac{M}{\rho+M_1M_2} \quad$ (B) $m = \large\frac{M}{\rho-M_1M_2} \quad$ (C) $m = \large\frac{\rho+M_1M_2} {M} \quad$ (D) $m = \large\frac{\rho-M_1M_2} {M} \quad$