M = molarity of the solution
m = molality of the solution
d = density of the solution (in g. ml^-1)
M₁ = gram molecular weight of solute
Which of the following relations is correct

Given that

Density of the solution =d (in gm/ml)

Molarity of the solution =M

Molar mass of the solute =M¹(in gm/mol)

Let's take 1000 ml of the solution, then 

Mass of the solution = Volume (ml) × density

                                   = 1000 ml × d gm/ml = 1000 d gm

Moles of solute =M × Volume = M×1lit= M moles  (Since, 1000ml=1liter)

∴   Mass of the solute = No. of moles× Molar  mass =MM¹gm

∴  Mass of the solvent = mass of the solution − mass of the solute                                                                 =(1000d−MM¹) gm 

$\mathrm{m}=\frac{\mathrm{no}. \mathrm{of} \mathrm{moles} \mathrm{of} \mathrm{solute}}{\mathrm{Kg} \mathrm{of} \mathrm{solvent}}$

$\therefore \mathrm{m}=\frac{\mathrm{M}\times 1000}{(1000\times \mathrm{d})-{\mathrm{MM}}^1}$