The compound that readily tautomerizes is

• Correct answer
  A

  $\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CO}_{2} \mathrm{C}_{2} \mathrm{H}_{5}$
• B

  $\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}$
• C

  $\mathrm{CH}_{3}^{3} \mathrm{COCH}_{2}^{2} \mathrm{CH}_{2}^{2} \mathrm{CH}_{3}$
• D

  $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCOC}\left(\mathrm{CH}_{3}\right)_{3}^{3}$

Solution

Aceto acetic ester has active methylene group.

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