When a metal rod ${M}$ is dipped into an aqueous colourless concentrated solution of compound ${N}$, the solution turns light blue. Addition of aqueous $\mathrm{NaCl}$ to the blue solution gives a white precipitate ${O}$. Addition of aqueous $\mathrm{NH}_3$ dissolves ${O}$ and gives an intense blue solution.
$1.$ The metal rod ${M}$ is
$(A)$ $\mathrm{Fe}$ $(B)$ $\mathrm{Cu}$ $(C)$ $\mathrm{Ni}$ $(D)$ $\mathrm{Co}$
$2.$ The compound ${N}$ is
$(A)$ $\mathrm{AgNO}_3$ $(B)$ $\mathrm{Zn}\left(\mathrm{NO}_3\right)_2$
$(C)$ $\mathrm{Al}\left(\mathrm{NO}_3\right)_3$ $(D)$ $\mathrm{Pb}\left(\mathrm{NO}_3\right)_2$
$3.$ The final solution contains
$(A)$ $\left[\mathrm{Pb}\left(\mathrm{NH}_3\right)_4\right]^{2+}$ and $\left[\mathrm{CoCl}_4\right]^{2-}$
$(B)$ $\left[\mathrm{Al}\left(\mathrm{NH}_3\right)_4\right]^{3+}$ and $\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}$
$(C)$ $\left[\mathrm{Ag}\left(\mathrm{NH}_3\right)_2\right]^{+}$and $\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}$
$(D)$ $\left[\mathrm{Ag}\left(\mathrm{NH}_3\right)_2\right]^{+}$and $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right]^{2+}$
Give the answer question $1,2$ and $3.$
