Concept:Profit sharing ratio changes when partners agree on a new basis for sharing profits due to changes in their contributions or circumstances.
Explanation:A partner's skill can justify a higher share, so I is valid.
Health status may affect a partner's workload, so II is valid.
Old age can reduce participation, so III is valid.
An increase in intangible assets is an accounting adjustment, not a reason for changing the ratio, so IV is not valid.
Thus, the correct combination is I, II and III.
Answer:C. I, II and III