Which of these is not a monomer for a high molecular mass silicone polymer?

The basic structural unit of silicates is:

1. SiO₄^4–

2. SiO₃^2–

3. SiO₄^2–

4. SiO

Which one of the following anions is present in the chain structure silicates?

1. $S{i}_2{O}_7^{6-}$

2. $\left(S{i}_2{O}_5^{2-}\right)n$

3. $\left(Si{O}_3^{2-}\right)n$

4. $Si{O}_4^{4-}$