The compound from the following with highest  ${\mathrm{p}}^{\mathrm{ka}}$ is  

All aromatic acids are more acidic than aliphatic acids except HCOOH.

In ${\mathrm{C}}_6{\mathrm{H}}_5–\mathrm{COOH}, –{\mathrm{C}}_6{\mathrm{H}}_5$ group show +M effect and –I effect due to ${\mathrm{sp}}^2$ hybridized carbon atoms of benzene ring.

– I effect is  due to ${\mathrm{sp}}^2$ carbons

 –I effect in this compound dominates +M effect.

$\therefore$Benzoic acid is more acidic than all aliphatic acids except HCOOH

$\therefore$HCOOH > ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$ > ${\mathrm{CH}}_3\mathrm{COOH}$

Comparing ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}, {\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_2\mathrm{COOH}, {\mathrm{CH}}_3\mathrm{COOH}$

${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH} > {\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_2\mathrm{COOH} > {\mathrm{CH}}_3\mathrm{COOH}$

$\therefore$$\mathrm{HCOOH} > {\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH} > {\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_2\mathrm{COOH} > {\mathrm{CH}}_3\mathrm{COOH}$

${\mathrm{p}}^{\mathrm{ka}} \mathrm{of} \mathrm{HCOOH} < {\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH} < {\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_2\mathrm{COOH} <{\mathrm{CH}}_3\mathrm{COOH}$