How is the retention of communications traffic data for law enforcement purposes addressed by European data protection law?

How is the retention of communications traffic data for law enforcement purposes addressed by European data protection law?
A . The ePrivacy Directive allows individual EU member states to engage in such data retention.
B . The ePrivacy Directive harmonizes EU member states’ rules concerning such data retention.
C . The Data Retention Directive’s annulment makes such data retention now permissible.
D . The GDPR allows the retention of such data for the prevention, investigation, detection or prosecution of criminal offences only.

Answer: A

Explanation:

Reference: https://www.law.kuleuven.be/citip/en/archive/copy_of_publications/440retention-of-traffic-data-dumortier-goemans2f90.pdf (9)