Which of the following is a disadvantage of using PAP authentication?

The correct choice highlights a significant drawback of Password Authentication Protocol (PAP) known as the insecure transmission of credentials. PAP transmits usernames and passwords in plain text over the network, which means that if the data is intercepted by an attacker, they can easily read the credentials without any decryption required. This vulnerability makes it a poor choice for secure environments where sensitive information is being transmitted, as it does not offer any form of encryption or protection for the credentials in transit.

Regarding the other choices, PAP does not typically require advanced configuration, making that option less relevant as a disadvantage. The protocol does not support encrypted passwords inherently; therefore, suggesting that it does is misleading. Additionally, PAP does not provide stronger security than Challenge Handshake Authentication Protocol (CHAP), which uses a more secure method of password verification involving a challenge-response mechanism that does not expose credentials directly during transmission.