Paragraph: When a metal rod M is dipped into an aqueous colourless...

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1. A\left[\mathrm{Pb}\left(\mathrm{NH}_3\right)_4\right]^{2+} and $\left[\mathrm{CoCl}_4\right]^{2-}$
2. B$\left[\mathrm{Al}\left(\mathrm{NH}_3\right)_4\right]^{3+}$ and \left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}
3. C$\left[\mathrm{Ag}\left(\mathrm{NH}_3\right)_2\right]^{+}$and \left[\mathrm{Co}\left(\mathrm{NH}_3\right)_4\right]^{2+}
4. D$\left[\mathrm{Ag}\left(\mathrm{NH}_3\right)_2\right]^{+}$and \left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right]^{2+}