WPA2 is the correct answer because it is the most secure form of Wi-Fi encryption currently available for personal and enterprise networks. It encrypts data transmitted over the network, protecting it from eavesdropping and unauthorized access. Open networks are unencrypted and thus insecure, making sensitive tasks risky. Captive portal and WEP are not directly related to the current encryption standards for secure communications; WEP is considered obsolete and easily compromised, while a captive portal is a web page that requires user action before network access is granted and doesn't guarantee encryption.