A retail credit score of above 680 is generally considered to be "prime.

Comprehensive and Detailed In-Depth Explanation:

In credit risk assessment, a "prime" borrower is one with a high credit score (e.g., above 680 on the FICO scale), indicating high credit quality and a low probability of default (PD). This classification is widely used in retail lending (e.g., mortgages, auto loans) to denote borrowers who are less risky, justifying lower interest rates. The Basel II framework, under the Internal Ratings-Based (IRB) approach, links credit quality to PD, where "prime" aligns with lower PD bands. Option D correctly pairs high quality (strong creditworthiness) with low risk of default. Option A is contradictory (low quality implies higher risk), Option B reverses the risk profile, and Option C describes "subprime" borrowers (typically below 620).

Exact Extract from Official Source:

BCBS, "Basel II: International Convergence of Capital Measurement and Capital Standards," June 2006, para. 211: "Under the IRB approach, banks must categorize banking-book exposures into broad classes of assets with different underlying risk characteristics… For retail exposures, this includes distinguishing between high-quality (low PD) and lower-quality (higher PD) borrowers."

GARP FRR Study Notes, Credit Risk Section: "Prime borrowers, typically with credit scores above 680, are considered high-quality obligors with a low likelihood of default, contrasting with subprime borrowers who exhibit higher risk profiles."