The compound $\mathrm{CoBr}(\mathrm{SO}{}_4)\cdot 5\mathrm{NH}{}_3$ (Co coordination number 6) gives no precipitate with excess $\mathrm{AgNO}{}_3$ but a white precipitate with $\mathrm{BaCl}{}_2$. Which statement is correct?

1. AIt is $[\mathrm{Co}(\mathrm{NH}{}_3){}_5\mathrm{SO}{}_4]\mathrm{Br}$; its ionisation isomer gives a pale-yellow precipitate with $\mathrm{AgNO}{}_3$ and a white precipitate with $\mathrm{BaCl}{}_2$.
2. BIt is $[\mathrm{Co}(\mathrm{NH}{}_3){}_5\mathrm{SO}{}_4]\mathrm{Br}$; its ionisation isomer gives a white precipitate with $\mathrm{BaCl}{}_2$ and none with $\mathrm{AgNO}{}_3$.
3. CIt is $[\mathrm{Co}(\mathrm{NH}{}_3){}_5\mathrm{Br}]\mathrm{SO}{}_4$; its ionisation isomer gives no precipitate with either $\mathrm{AgNO}{}_3$ or $\mathrm{BaCl}{}_2$.
4. DIt is $[\mathrm{Co}(\mathrm{NH}{}_3){}_5\mathrm{Br}]\mathrm{SO}{}_4$; its ionisation isomer gives a pale-yellow precipitate with $\mathrm{AgNO}{}_3$ and none with $\mathrm{BaCl}{}_2$.