C. - the question is about the greatest threat to its independence. The former - merely supporting - function in the development of the general KPIs of the organization is certainly the weaker threat to his independence than a current development of KPIs for the assessment of the internal audit team with his current, current activity as Lead Auditor, obviously within the same organization, i.e. his own team. In B.'s case, I see no compelling connection between his former support for the general organizational KPIs and the risk-related KPIs that are now recommended. If so, this should be specified more precisely in the question. This option is also weaker in the ranking compared to C.