Robert has pure samples of both D-ribose and D-arabinose, but he forgot to label them. He only has some nitric acid, the reagents for a Wohl degradation, and a polarimeter (an instrument for measuring optical activity) in his lab. In approximately 50 words or less, explain how Robert can determine which sample is which without using any additional resources. If it is not possible, clearly state so and explain why it is not possible in approximately 50 words or less.