A white solid Y dissolves in water to give an alkaline solution and imparts a persistent golden-yellow flame. It swells on heating and fuses to a glassy mass. When Y is warmed with ethanol and conc. $\mathrm{H}{}_2\mathrm{SO}{}_4$ and the vapour is ignited, it burns with a green-edged flame. Y and the number of ethanol molecules that react with each boron atom to form the volatile ester are respectively

1. A$\mathrm{Na}{}_2\mathrm{CO}{}_3\cdot 10\mathrm{H}{}_2\mathrm{O}$ ; 3
2. B$\mathrm{Na}{}_2\mathrm{B}{}_4\mathrm{O}{}_7\cdot 10\mathrm{H}{}_2\mathrm{O}$ ; 3
3. C$\mathrm{H}{}_3\mathrm{BO}{}_3$ ; 1
4. D$\mathrm{Na}{}_2\mathrm{B}{}_4\mathrm{O}{}_7\cdot 10\mathrm{H}{}_2\mathrm{O}$ ; 4