Which among the following oxoacids of phosphorous will have $\mathrm{P}-\mathrm{O}-\mathrm{P}$ bonds?

I. $\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{5}$

II. $\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}$

III. $\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7}$

IV. $\left(\mathrm{HPO}_{3}\right)_{3}$

What are $X$ and $Y$ respectively in the following reactions ?

$ X \stackrel{\mathrm{CO}}{\longleftarrow} \mathrm{~B}_{2} \mathrm{H}_{6} \xrightarrow[\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{O}]{\mathrm{NaH}} Y $

Which of the following statements are correct?

(i) $\mathrm{CCl}_{4}$ undergoes hydrolysis easily

(ii) Diamond has directional covalent bonds

(iii) Fullerene is thermodynamically most stable allotrope of carbon

(iv) Glass is a man-made silicate

The correct answer is