Silicon is second most abundant element occurring in earth crust. It is always found in combined state. Silicon exists in two allotropic forms,amorphous & crystalline. The compounds of silicon are carborundum, silicon, silicate,glass etc.
Silicones are organosilicon polymer & silicates are metal derivatives of silicic acid. While carborundum are obtained by heating mixture of sand, carbon & common salt.
The structural unit of silicates is

Options

A. `SiO_2`
B. `SiO_4^(4-)`
C. `SiO_3^(2-)`
D. `SiO_2^(2-)`

Answer

B