The correct order of acidic strength of the carboxylic acid is

The reaction, ${\mathrm{CH}}_3\mathrm{COOH}+{\mathrm{Cl}}_2\stackrel{\mathrm{P}}{⟶}{\mathrm{ClCH}}_2\mathrm{COOH}+\mathrm{HCl}$ is called

Final product (B) obtained in the following sequence of reactions is

${\mathrm{CH}}_2=\mathrm{CH}-{\mathrm{CH}}_2-\mathrm{CN}\underset{\left(\mathrm{ii}\right){\mathrm{H}}_2\mathrm{O}}{\overset{\left(\mathrm{i}\right) \mathrm{DIBAL} -\mathrm{H}}{\to }}\mathrm{A}\underset{\left(\mathrm{ii}\right)\mathrm{KOH}/\mathrm{\Delta }}{\overset{\left(\mathrm{i}\right) {\mathrm{NH}}_2{\mathrm{NH}}_2}{\to }}\mathrm{B}$

Which of the following pairs can be distinguished by Fehling test?