Why d-glucose and d-fructose and d-manose give rise to same osazone?

D-glucose, D-fructose, and D-mannose can form the same osazone because they all contain the same functional groups that react with phenylhydrazine to produce osazones. The osazone formation involves the carbonyl group of the reducing sugars reacting with phenylhydrazine, leading to the same structure of the resulting osazone compound due to the rearrangement and isomerization of these sugars. Consequently, despite their structural differences, the final osazone has the same molecular characteristics and thus appears identical in tests.