Metals are extracted by other methods through the formation of complexes. The complexes formed in these methods are: $I$: Cyanide process,$II$: Mond process,$III$: Photographic fixing process.

• A
  $(I) [Ag(NH_3)_2]Cl, (II) Ni(CO)_4, (III) [Ag(CN)_2]^{-}$
• B
  $(I) [Cd(CN)_4]^{2-}, (II) Ni(CO)_4, (III) [Ag(S_2O_3)_2]^{3-}$
• C
  $(I) [Ag(CN)_2]^{-}, (II) Ni(CO)_4, (III) [Ag(S_2O_3)_2]^{3-}$
• D
  $(I) [Ag(CN)_2]^{-}, (II) [Ag(S_2O_3)_2]^{3-}, (III) Ni(CO)_4$