Explanation:

✅ D. All of the above, forming a multi-layered approach to data security during and after migration
Protecting sensitive customer information during data migration requires a comprehensive, multi-layered security approach. Data encryption at rest and in transit ensures data is secure during transfer and storage. User permissions and field-level security restrict access within Salesforce post-migration. Data anonymization or pseudonymization masks sensitive data to minimize exposure risks. Combining these mechanisms provides end-to-end protection, addressing vulnerabilities at different stages of the migration process and ensuring compliance with data security standards.

❌ A. Data encryption at rest and in transit via SSL/TLS protocols
Encryption at rest and in transit using SSL/TLS protocols is critical for securing data during transfer and storage in Salesforce. However, it only addresses data protection during movement and storage, not access control or data exposure risks. Without additional measures like user permissions or data masking, sensitive information could still be accessed or exposed, making encryption alone insufficient.

❌ B. User permissions and field-level security restricting access to sensitive data within Salesforce
User permissions and field-level security in Salesforce are essential for controlling who can access sensitive data post-migration. However, these controls apply within the Salesforce environment and do not protect data during the migration process or prevent exposure of sensitive information in transit or storage. They are a key component but not comprehensive without encryption and anonymization.

❌ C. Data anonymization or pseudonymization masking sensitive information during migration and storage
Data anonymization or pseudonymization masks sensitive customer information, reducing the risk of exposure during migration and storage. While effective for compliance and minimizing data breaches, it does not address secure data transfer or access control post-migration. Without encryption and user permissions, this approach alone cannot fully protect data throughout the migration lifecycle.

Reference:
🔗 Salesforce Help: Data Encryption
🔗 Salesforce Help: Set Field-Level Security
🔗 Salesforce Help: Data Protection and Privacy