Certain car paints include minute flakes of silica, $\text{SiO}_2$. In the solid structure of $\text{SiO}_2$: - every silicon atom is bonded to $x$ oxygen atoms, - every oxygen atom is bonded to $y$ silicon atoms, - each bond is a $z$ type bond. Which combination of $x$, $y$ and $z$ is correct for these statements?
- A$x=2$, $y=1$, covalent
- B$x=2$, $y=1$, ionic
- C$x=4$, $y=2$, covalent
- D$x=4$, $y=2$, ionic