b
Recall that presence of electron - withdrawing group increase, while presence of electron - releasing group decrease the acidity of carboxylic acids.

\(\mathop {ClC{H_2}COOH}\limits_{(electron\,- \,withdrawing\,gp.)}  > \) \(\begin{array}{*{20}{c}}
  {O\,\,\,} \\ 
  {||\,\,\,} \\ 
  {H - C - OH} 
\end{array}\) \(>\) \(\begin{array}{*{20}{c}}
  {\,\,\,\,O\,\,\,} \\ 
  {\,\,\,\,||\,\,\,} \\ 
  {C{H_3} - C - OH} 
\end{array}\) \(>\) \(\begin{matrix}
   \,\,\,O\,\,\,  \\
   \,\,\,||  \\
   {{C}_{2}}{{H}_{5}}-C-OH  \\
\end{matrix}\)

                                                        (Electron - releasing charecter  increase from left to right)