' $X$ ' on hydrolysis gives two products. One of them is solid. What is ' $X$ '?

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 $x^{-}$?

Identify the correct statements

i. Oxidation of $\mathrm{NaBH}_4$ with $\mathrm{I}_2$ gives $\mathrm{B}_2 \mathrm{H}_6$

ii. $\mathrm{B}_2 \mathrm{H}_6$ burns in oxygen and releases an enormous amount of energy

iii. $\mathrm{B}_2 \mathrm{H}_6$ on hydrolysis gives a tribasic acid