Which of the following are correct?

i. Basic structural unit of silicates is $-R_2 \mathrm{SiO}-$

ii. Silicones are biocompatible

iii. Producer gas contains CO and $\mathrm{N}_2$

The correct option is

Which of the following reactions give phosphine?

i. Reaction of calcium phosphide with water

ii. Heating white phosphorous with concentrated NaOH solution in inert atmosphere

iii. Heating red phosphorous with alkali

Observe the following stoichiometric equation

$$ \mathrm{P}_4+3 \mathrm{OH}^{-}+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{PH}_3+3 x^{-} $$

What is the conjugate acid of $x^{-}$?