Alcohol Phenols And Ethers

Identify substrate ' $A$ ' in the following reaction.

$\mathrm{A}+\mathrm{CO}_2 \xrightarrow[6 \text { atm }]{398 \mathrm{~K}}$ Sodium salicylate $\xrightarrow{\mathrm{H}_3 \mathrm{O}^{+}}$Salicylic acid