Match the compounds in Column I with their characteristic...

A-r; B-p, q; C- p, q, r; D-p Sodium fusion extract gives Prussian blue when nitrogen is present alongwith carbon. Phenolic group and carboxylate gives positive $\mathrm{FeCl}_3$ test - white precipitate comes with $\mathrm{AgCl}$. $\text{ Hydrazone formation occurs effectively at } \mathrm{pH} \approx$4.5 $\text{. The reaction proceeds in that }$condition only when $\mathrm{H}^{+}$concentration is merely sufficient to activate. As $\mathrm{H}^{+}$concentration raises, sufficient molecule of hydrazone gets converted into hydrazonium which is not nucleophilic and reaction becomes impossible. Further, low concentration of $\mathrm{H}^{+}$(in the case of hydrolysis of 2, 4-dinitrophenyl hydrazonium bromide) is not effective to proceed elimination (rate determining step). $<img src="/api/proxy-image?url=https$ \\ If it is assumed that the given hydrazonian bromiate is the result as salt main $\mathrm{HBr}$ is used as acid catalyst. Remember! hydrazone formation involves first addition and then elimination (res). In the second step substitution dominates over elimination ( $\mathrm{HBr}$ is not a dehydrating reagent mutually).