| List $I$ Vitamin | List $II$ Deficiency disease |
| $A$ Vitamin $A$ | $I.$ Beri-Beri |
| $B$ Thiamine | $II.$ Cheilosis |
| $C$ Ascorbic acid | $III.$ Xeropthalmia |
| $D$ Riboflavin | $IV.$ Scurvy |
Choose the correct answer from the options given below:
Product $(A)$ of above reaction is