X is a salt containing one of the halogens chlorine, bromine, iodine, or astatine (proton number $85$). The reaction scheme below gives a sequence of reactions starting with a solution of X as the initial reagent: X $\xrightarrow[\text{AgNO}_3(aq)]{\text{HNO}_3(aq)}$ a precipitate $\xrightarrow[\text{dilute } \text{NH}_3(aq)]{\text{excess}}$ a colourless solution $\xrightarrow[\text{HNO}_3(aq)]{\text{excess}}$ a precipitate. Which substance could X be?
- Asodium chloride
- Bsodium bromide
- Cpotassium iodide
- Dpotassium astatide