An ore X on roasting in excess air gives a pungent colourless gas and a white oxide (yellow when hot) that dissolves in both acids and alkalis. The oxide is heated with coke at 1673 K and the metal distils out. Which choice correctly names the ore and explains why the metal appears as vapour?

1. A$\mathrm{ZnCO}{}_3$; zinc boils at 1180 K, which is below 1673 K
2. B$\mathrm{PbS}$; lead boils at 1180 K, which is below 1673 K
3. C$\mathrm{ZnS}$; zinc melts at 1180 K, so a liquid flows out
4. D$\mathrm{ZnS}$; zinc boils at 1180 K, which is below 1673 K