正解:C
The best way to reduce the risk of disruption from an emergency system change is to confirm rollback plans are in place. According to the CISM Review Manual, having an effective rollback (or backout) plan ensures that if the emergency change causes unexpected issues, the organization can quickly revert to a known, stable state. This minimizes downtime and impact to business operations. Approval and communication are important, but only a rollback plan directly addresses risk reduction during unexpected disruptions.
Reference:ISACA CISM Review Manual, 16th Edition, Page 210, "Change Management - Rollback Planning".