Comprehensive and Detailed In-Depth Explanation:
Stress testing evaluates a credit portfolio's resilience under adverse scenarios (e.g., economic downturns), quantifying impacts on defaults, losses, and capital adequacy. Option D is correct-Basel II's Pillar 2 mandates stress testing for unexpected outcomes. Option A (common situations) describes standard modeling, not stress testing. Option B (probabilistic expectations) aligns with VaR, not stress testing's focus on extremes. Option C (optimizing migration) is unrelated to stress testing's purpose.
Exact Extract from Official Source:
* BCBS, "Basel II: International Convergence of Capital Measurement and Capital Standards," June
2006, para. 434: "Stress testing is a critical tool for credit risk assessment, enabling banks to quantify the impact of adverse and unexpected scenarios on their credit portfolios and capital levels."
* GARP FRR Study Notes, Credit Risk Section: "Stress testing assesses the effect of severe, unexpected events on credit losses and capital, distinguishing it from routine risk modeling." Reference:BCBS, "Basel II," para.434; GARP FRR Study Notes, Credit Risk Section.