Which one of the following tests is used for the identification of functional groups in organic compounds does not use…

Step 1: Reviewing Copper Tests — Many carbohydrate and protein tests use $\ce{Cu^2+}$ ions. These include $\text{Barfoed's, Benedict's}$, and the $\text{Biuret test}$.

Step 2: Finding the Exception — $\text{Seliwanoff's test}$ is specifically used to distinguish aldoses from ketoses using resorcinol in concentrated $\ce{HCl}$.

Step 3: Conclusion — Since $\text{Seliwanoff's test}$ relies on acid-catalyzed dehydration rather than copper reduction, it is the correct answer. Correct option is (b).

Key Point: Barfoed and Benedict tests involve the reduction of soluble $\ce{Cu^2+}$ (blue) to insoluble $\ce{Cu2O}$ (red).