Within the solid structure of $\text{SiO}_2$, each silicon atom forms bonds with $x$ oxygen atoms, each oxygen atom forms bonds with $y$ silicon atoms, and every bond is of type $z$. Which combination of $x$, $y$ and $z$ is correct in 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