Option C is correct. Best practices in economic capital governance dictate that there should be a robust contingency plan and policy in place. This includes incorporating explicit escalation procedures so that breaches in economic capital limits or policy deviations are appropriately reported and managed at higher levels of governance.

• Option A is incorrect because while business unit managers should challenge assumptions, final approval of capital models should generally lie with an independent risk oversight committee or the board of directors, not the business units themselves, to ensure objectivity and avoid conflicts of interest.
• Option B is incorrect because simply summing exposures ignores diversification benefits across different risk types, which is a fundamental component of an accurate economic capital framework.
• Option D is incorrect because utilizing third-party macroeconomic scenarios is a widely accepted and often encouraged practice. It provides an independent, expert perspective for stress testing economic capital models.