X, Y and Z are compounds made from three elements in Period 3. The table shows how well they conduct electricity. Conductivity of the compound when molten: X good, Y does not conduct, Z does not conduct. Conductivity of the mixture formed after the compound is added to water: X good, Y good, Z does not conduct. What could X, Y and Z be?
- AX = $\text{Al}_2\text{O}_3$, Y = $\text{SiCl}_4$, Z = $\text{NaF}$
- BX = $\text{NaF}$, Y = $\text{Al}_2\text{O}_3$, Z = $\text{SiCl}_4$
- CX = $\text{NaF}$, Y = $\text{SiCl}_4$, Z = $\text{SiO}_2$
- DX = $\text{SiCl}_4$, Y = $\text{Al}_2\text{O}_3$, Z = $\text{SiO}_2$