In which mode of expression, the concentration of solution remains independent of temperature?

We know that, Molarity $=\frac{No. of moles of solute}{Volume of solution in litres}$

                        Normality $=\frac{No. of gram equivalents}{Volume of solution in litres}$

And also, Normality = Molarity $\times {\mathrm{n}}_{\text{factor }}$.

               Formality $=\frac{\text{ No. of gram}\text{ equivalents}}{\text{ Volume(Litres) }}$

               Molality  $=\frac{Moles of solute}{Mass of solvent in kg}$

 Molarity depends on temperature.

$\mathrm{M}\propto \frac{1}{ \mathrm{V}}\propto \frac{1}{ \mathrm{T}}$

$\mathrm{V}=$ $Volume$  ,  $\mathrm{T}=$ $Temperature$

If molarity is dependent on temperature, Normality is also dependent on temperature.

Similarly, Formality also depends on Volume.

Therefore, Formality is also dependent on temperature.

$\mathrm{V}\propto \mathrm{T}$

Molality is the one which depends upon the mass of the solute and the solvent.

The mass is independent of temperature.

Thus, molality is independent of temperature.

Hence, option (d) is correct.