The equation which is balanced and represents the correct product(s) is:

Question

( A ) $CuSO_4 + 4 KCN \to K_2 [Cu(CN)_4] + K_2SO_4$
( B ) $[Mg(H_2O)_6 ]^{2+} + (EDTA)^{4-} \xrightarrow{excess\; NaOH} [Mg (EDTA)]^{2+} +6H_2O$
( C ) $Li_2O + 2 KCl \to 2LiCl + K_2O$
( D ) $[CoCl(NH_3)_5]^+ + 5H^+ \to Co^{2+} + 5 NH_4^+ + Cl^-$