The correct order of acid strength of the following carboxylic acids is -

• A

  $\mathrm{I}>\mathrm{I}\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{V}$
• B

  $\mathrm{I}\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{I}>\mathrm{I}>\mathrm{I}\mathrm{V}$
• C

  $\mathrm{I}\mathrm{I}>\mathrm{I}>\mathrm{I}\mathrm{V}>\mathrm{I}\mathrm{I}\mathrm{I}$
• Correct answer
  D

  $\mathrm{I}>\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{V}$

Solution

Acidic strength $\propto$ stability of conjugate chain Order of Acidic strength $\Rightarrow \boxed{\text{I}>\text{II}>\text{III}>\text{IV}}$

Hence, the correct answer is option: 'D'.