Oxidation And Reduction Reactions

Concept: Disproportionation = same element oxidized and reduced

Step 1: In reaction I, N has different oxidation states initially.

Step 2: In reaction II, N again starts with different oxidation states.

Step 3: In reaction III, P changes but no simultaneous oxidation and reduction of same species.

Step 4: Hence none are true disproportionation reactions.
Conclusion:
Disproportionation not shown in all (I, II, III)