Explanation
Pseudonymization is a technique that replaces direct identifiers in a data set with pseudonyms or artificial identifiers that do not reveal the identity of the data subjects. Pseudonymization reduces the linkability of the data set with the original identity of the data subjects and thus enhances the privacy and security of the data.
However, pseudonymization is not irreversible and the original identity can be re-established if the pseudonym or key is compromised. Therefore, it is important to keep the identifier separate and distinct from the data it protects and to apply additional security measures to safeguard the identifier. The other options are not relevant to pseudonymization1, p. 74-75 References: 1: CDPSE Review Manual (Digital Version)

However, the risks associated with long-term retention have compelled organizations to consider alternatives; one is data archival, the process of preparing data for long-term storage. When organizations are bound by specific laws to retain data for many years, archival provides a viable opportunity to remove data from online transaction systems to other systems or media.