Ethylene glycol reacts with excess of $\mathrm{P}\mathrm{C}{\mathrm{l}}_5$ to give

Glycerol on heating with concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$ form one mole each of formaldehyde and acetaldehyde.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

Glycerol on heating with ${\mathrm{KHSO}}_4$ forms