Comprehensive and Detailed Step-by-Step Explanation: Determining downtime costs requires understanding the financial and operational impact on the business. * A. Fault tree analysis: Primarily used for identifying the root causes of failures, not for assessing downtime costs. * B. Cost-benefit analysis: Compares the costs and benefits of implementing controls but does not specifically address downtime. * C. Return on investment (ROI) analysis: Evaluates the financial return of an investment rather than the cost of an outage. * D. Business impact analysis (BIA): This is the BEST answer because a BIA identifies the effects of a disruption on critical business functions and quantifies the financial impact, including downtime costs. Reference: CISM Job Practice Area 3 (Information Security Program Development and Management) discusses BIA as a key component in understanding the financial implications of downtime.