Explanation
MACsec, defined in 802.1AE, provides MAC-layer encryption over wired networks by using out-of-band methods for encryption keying. The MACsec Key Agreement (MKA) Protocol provides the required session keys and manages the required encryption keys. MKA and MACsec are implemented after successful authentication using the 802.1x Extensible Authentication Protocol (EAP-TLS) or Pre Shared Key (PSK) framework.
Reference:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/16-9/configuration_guide/sec/

Explanation
Scrypt is safer than MD5, so answer A is wrong and answer D is correct
R1(config)#username user secret ?0 Specifies an UNENCRYPTED secret will follow5 Specifies a MD5 HASHED secret will follow8 Specifies a PBKDF2 HASHED secret will follow9 Specifies a SCRYPT HASHED secret will follow<0-9> Encryption types not explicitly specifiedLINE The UNENCRYPTED (cleartext) user secretLINE The UNENCRYPTED (cleartext) user secret Reference: https://community.cisco.com/t5/networking-documents/understanding-the-differences-between-the-c

Explanation
HTTP Status 204 (No Content) indicates that the server has successfully fulfilled the request and that there is no content to send in the response payload body.