The table presents the physical properties of four substances, W, X, Y and Z. What are the identities of W, X, Y and Z?
- AW: $\text{MgO}$, X: $\text{C}_2\text{H}_5\text{Br}$, Y: $\text{Fe}$, Z: $\text{Al}_2\text{O}_3$
- BW: $\text{MgO}$, X: $\text{HCl}$, Y: $\text{K}$, Z: $\text{Al}_2\text{O}_3$
- CW: $\text{NaF}$, X: $\text{C}_2\text{H}_5\text{Br}$, Y: $\text{Fe}$, Z: $\text{SiO}_2$
- DW: $\text{NaF}$, X: $\text{HCl}$, Y: $\text{K}$, Z: $\text{SiO}_2$