(a) Which of the D-aldopentoses will give optically active aldaric acids on oxidation with HNO₃?

(b) Which of the D-aldotetroses will give optically active aldaric acids on oxidation with HNO₃?

(c) Sugar X is known to be a D-aldohexose. On oxidation with HNO₃ X gives an optically inactive aldaric acid. When X is degraded to an aldopentose, oxidation of the aldopentose gives an optically active aldaric acid. Determine the structure of X.

(d) Even though sugar X gives an optically inactive aldaric acid, the pentose formed by degradation gives an optically active aldaric acid. Does this finding contradict the principle that optically inactive reagents cannot form optically active products?

(e) Show what product results if the aldopentose formed from degradation of X is further degraded to an aldotetrose. Does HNO₃ oxidize this aldotetrose to an optically active aldaric acid?