A white solid A decomposes on strong heating to a solid B and a gas C. B reacts vigorously with water giving a suspension D used in whitewashing. Passing C into D first gives A as a milky turbidity, and excess C makes the turbidity clear, giving E. Which statement is correct?

1. AE is $\mathrm{Ca}(\mathrm{HCO}{}_3){}_2$, a stable solid that can be isolated by evaporating the solution.
2. BE is $\mathrm{CaO}$, formed by the reaction of C with D.
3. CE is $\mathrm{Ca}(\mathrm{HCO}{}_3){}_2$, which exists only in solution, and boiling its solution re-precipitates A.
4. DE is $\mathrm{Ca}(\mathrm{HCO}{}_3){}_2$, and boiling its solution precipitates $\mathrm{Ca}(\mathrm{OH}){}_2$.