The correct protocol is EAP-Transport Layer Security (TLS) because it ensures a high level of security by providing mutual authentication, where both the client and the server confirm each other's identity. EAP-TLS uses the secure and standardized TLS protocol to encapsulate the authentication process and can be transported over various network protocol mechanisms, which makes it highly suitable for diverse environments, including those required for BYOD policies. EAP-MD5 is a simpler option that is less secure and does not provide mutual authentication, making it a less suitable choice. EAP-Flexible Authentication via Secure Tunneling (FAST) does offer mutual authentication and was designed to be an alternative to systems that use certificates, but it's not the most appropriate option for environments that use various network transports. EAP-Generic Token Card (GTC) is primarily used for token-based authentication and does not provide mutual authentication on its own without being combined with other security measures.