How current must anti-malware solutions be kept?

• A.Signature databases must be refreshed manually after each quarterly ASV scan, with the QSA reviewing the definitions and the update history before deployment
• B.Anti-malware engines must be replaced with a newly certified product from the vendor list once a year, with signatures and engine versions frozen between replacements
• C.Anti-malware mechanisms must be kept current with the latest signatures, updates, and definitions through automatic updates
• D.Anti-malware definitions must be updated at least monthly, with the update window logged and approved