Identify the product ' $\mathrm{B}$ ' in following reaction. $2 \mathrm{CH}_3 \mathrm{CHO} \stackrel{\text { dil.NaOH }}{\longrightarrow} \mathrm{A} \underset{-\mathrm{H}_2 \mathrm{O}}{\stackrel{\Delta}{\longrightarrow}} \mathrm{B}$

• A

  But-3-enal
• B

  3-Hydroxyl butanal
• Correct answer
  C

  But-2-enal
• D

  4-Hydroxyl butanal

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