Concept:By Kohlrausch’s law, the limiting molar conductivity of a weak electrolyte equals the sum of the limiting ionic conductivities of its constituent ions.Explanation:For NH4OH,Λm(NH4OH)0=λNH4+0+λOH−0Write Kohlrausch equations for the given strong electrolytes:Λm(NH4Cl)0=λNH4+0+λCl−0Λm(NaOH)0=λNa+0+λOH−0Λm(NaCl)0=λNa+0+λCl−0Now combine them as:Λm(NH4Cl)0+Λm(NaOH)0−Λm(NaCl)0=(λNH4+0+λCl−0)+(λNa+0+λOH−0)−(λNa+0+λCl−0)The λNa+0 and λCl−0 terms cancel out, giving:λNH4+0+λOH−0=Λm(NH4OH)0Thus the required expression is obtained.Answer:Option BΛm(NH4Cl)0+Λm(NaOH)0−Λm(NaCl)0