A customer has supplied personal information to a bank to facilitate opening an account.

Comprehensive and Detailed Explanation:

Data privacy principles — particularly under GDPR and similar frameworks — emphasize data minimization, purpose limitation, and lawful processing. Once a customer closes an account and the statutory retention period ends, the organization should destroy personal information (A) to prevent misuse. Sharing data with affiliates (B) without explicit consent violates purpose limitation. Retaining data for convenience (C) is not legally justified. Using personal information for external research (D) is only valid if explicit consent was granted, but this is not described. Thus, the correct approach is Option A — delete data when it is no longer needed or legally required, ensuring compliance with privacy laws.