When heated, compound X gives off carbon dioxide gas and produces a white solid, Y. Neither X nor Y dissolves in water. Compound Y is used as a refractory lining for kilns. What is compound X?
- A$\text{CaCO}_3$
- B$\text{CaO}$
- C$\text{MgCO}_3$
- D$\text{MgO}$