Calculate the oxidation number of Cr in $\mathrm{CrO}_4^{2-}$ ion and $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ respectively.

Identify the monomer used to obtain a polymer that resembles the wool.

Which from following is a correct stability order of complex formed by metal ions if the ligand remains same?

Aldol condensation reaction is