Which of the following must an organization conduct to ensure compliance with PCI DSS?

An organization must conduct regular employee training to ensure compliance with PCI DSS because human error is a significant factor in security breaches. Training helps employees understand their roles in protecting cardholder data, recognize phishing attempts, and comply with internal security policies. This knowledge is crucial for maintaining a culture of security within the organization and ensuring that employees can identify and respond to security threats effectively.

While other options like vendor management reviews, penetration tests, and security audits play important roles in a comprehensive security posture, they do not directly address the human element that employee training targets. Regular education on security practices is essential for reinforcing the protocols that protect sensitive cardholder information and ultimately supporting overall compliance with PCI DSS.