Which of the following wireless security features provides the best wireless security mechanism?

WEP uses a weak 40-bit or 104-bit static key with a flawed RC4 implementation and short 24-bit IV, making it trivially crackable with tools like AirSnort.

WPA improves on WEP with TKIP and per-packet keys, but without specifying an authentication method it defaults to Pre-Shared Key mode, which is weaker than 802.1X-based authentication.

WPA with Pre-Shared Key (WPA-Personal) uses a single passphrase shared across all users, meaning compromise of one device or user exposes the entire network.

WPA with 802.1X (also called WPA-Enterprise) uses an external RADIUS authentication server to validate each user with unique credentials, eliminating the shared-secret vulnerability. It generates per-session, per-user dynamic encryption keys via the EAP framework, making key compromise far less likely than static or shared-key approaches. This combination of mutual authentication and dynamic keying represents the strongest security posture among the choices.