Option D is correct because Platform Shield Encryption allows you to encrypt standard fields and use them in workflow rules. Platform Shield Encryption uses AES 256-bit encryption to protect sensitive data atrest, while preserving platform functionality12

Option A is incorrect because Cryptography Class is a set of Apex methods for creating digests, message authentication codes, signatures, and encryption. It does not provide a way to encrypt standard fields or use them in workflow rules3

Option B is incorrect because Data Masking is a feature that replaces sensitive data in sandboxes with dummy data. It does not encrypt data in production or allow the use of encrypted data in workflow rules45

Option C is incorrect because Classic Encryption is a feature that encrypts custom fields with 128-bit AES encryption. It does not support standard fields or workflow rules67