Which one of the following has the highest molar conductivity?

The molar conductivity of an electrolyte solution is defined as its conductivity ( $\mathrm{k}$ ) divide by its molar concentration (C). i.c., Molar conductivity $(\lambda)=\frac{\kappa}{C}$ The measurement of molar conductivity of solutions of coordinate compounds helps to estimate the number of ions furnished by compound in the solution. By comparing molar conductivity we are able to predict the number of ions present in the solution. More be the number of ions, more is the value of molar conductivity. $\because$ Potassium hexacynoferrate (II), give maximum number of ions. Thus, (d) is the correct answer.