Identify product C in following conversion:
m-Hydroxy Benzaldehyde $\xrightarrow{\text{[Protection of -OH group]} \, \text{C}_6\text{H}_5\text{CH}_2\text{Cl}} \text{A} \xrightarrow{\text{[O]}} \text{B} \xrightarrow{\text{[deprotection of -OH group]}} \text{C}$