Limiting molar conductivity of $NH_4OH$ (i.e. $\Lambda^o_m (NH_4 OH))$ is equal to

Question

( A ) $\Lambda^o_m (NH_4OH) + \Lambda^o_m (NH_4Cl) - \Lambda^o_m (HCl)$
( B ) $\Lambda^o_m (NH_4Cl) + \Lambda^o_m (NaCl) - \Lambda^o_m (NaOH)$
( C ) $\Lambda^o_m (NaOH) + \Lambda^o_m (NaCl) - \Lambda^o_m (NH_4Cl)$
( D ) $\Lambda^o_m (NH_4Cl) + \Lambda^o_m (NHOH) - \Lambda^o_m (NaCl)$