The equivalent conductance of NaCl at concentration C and at infinite dilution are λc and λ∞ is given as: (where the constant B is positive)

λc = λ∞ − (B)√C (for strong electrolyte)
It is according to Debye Huckel equation for strong electrolyte (Relation between λc and λ∞ is given by Debye Huckel limiting law)
Option C is correct.