Which from following groups is selected as principal functional group for nomenclature of a polyfunctional compound according to IUPAC system?

Identify the structure of $\mathrm{XeF}_4$ molecule from following.

Calculate $\left[\mathrm{H}_3 \mathrm{O}^{+}\right]$in 0.02 M solution of monobasic acid if dissociation constant is $1.8 \times 10^{-5}$.

Which from following statements is NOT true according to principles of green chemistry?