正解:C
Risk ownership should be assigned when the risk is identified (C). CISM emphasizes early assignment of ownership to ensure accountability for analysis, treatment decisions, and monitoring throughout the risk lifecycle. Waiting until treatment execution (A) delays accountability, while asset ownership (B) or vulnerability identification (D) alone does not ensure ownership of the broader business risk. Early ownership ensures risks are properly evaluated, escalated, and managed in line with risk appetite.
References: ISACA CISM Review Manual (Risk management-risk lifecycle and accountability); CISM Exam Content Outline (Domain 1).