A solution contains $0.010\mathrm{M}$ each of $\mathrm{Cl}{}^{-}$, $\mathrm{Br}{}^{-}$ and $\mathrm{I}{}^{-}$. Dilute $\mathrm{AgNO}{}_3$ is added slowly (ignore volume change). Given $K_{sp}$: $\mathrm{AgCl}$ $1.8\times 10^{-10}$, $\mathrm{AgBr}$ $5.0\times 10^{-13}$, $\mathrm{AgI}$ $8.5\times 10^{-17}$. State the order of precipitation and the concentration of iodide remaining when $\mathrm{AgCl}$ just begins to precipitate.

1. A$\mathrm{I}{}^{-}$, $\mathrm{Br}{}^{-}$, $\mathrm{Cl}{}^{-}$; $4.7\times 10^{-9}\mathrm{M}$
2. B$\mathrm{Cl}{}^{-}$, $\mathrm{Br}{}^{-}$, $\mathrm{I}{}^{-}$; $4.7\times 10^{-9}\mathrm{M}$
3. C$\mathrm{I}{}^{-}$, $\mathrm{Br}{}^{-}$, $\mathrm{Cl}{}^{-}$; $6.3\times 10^{-12}\mathrm{M}$
4. D$\mathrm{I}{}^{-}$, $\mathrm{Br}{}^{-}$, $\mathrm{Cl}{}^{-}$; $8.5\times 10^{-15}\mathrm{M}$