What are X and P in the following reaction sequence?

Step-by-step solution

The given reaction is an intramolecular Cannizzaro reaction of a dialdehyde having -CHO and -CDO groups. In the first step, the hydroxide ion ( OH^- ) attacks the carbonyl carbon. The -CHO carbon is slightly more electrophilic than the -CDO carbon due to the +I effect of deuterium. More importantly, in the rate-determining step, the transfer of a hydride ion ( H^- ) is faster than the transfer of a deuteride ion ( D^- ) due to the primary kinetic isotope effect ( k_H > k_D ). Therefore, the OH^- attacks the -CHO gr