Refer to the exhibit.

The correct configuration is option C because Cisco IOS XE restricts inbound protocols on VTY lines with thetransport inputcommand. Cisco’s Catalyst 9800 best-practice guidance states that administrators should confirm SSH is enabled and Telnet is disabled for better controller security, and that the Catalyst 9800 follows standard Cisco IOS XE behavior for enabling or disabling Telnet and SSH. Cisco IOS XE SSH documentation explicitly showsline vty line_number [ending_line_number]followed bytransport input ssh, and explains that this prevents non-SSH Telnet connections, limiting access to SSH only.

The existing exhibit already includes the SSH prerequisites: hostname, domain name, RSA key generation, AAA new-model, a default login method using local credentials, and a local privileged user. The missing VTY configuration must therefore apply that default AAA login list to the VTY lines withlogin authentication defaultand restrict inbound transport to SSH. Cisco AAA documentation confirms thatlogin authentication defaultapplies the configured default authentication list to the line or set of lines. Option A is incomplete and does not explicitly permit SSH. Option B uses invalid syntax. Option D omits the requiredinputkeyword. Reference topics:Catalyst 9800 secure management, VTY access control, SSH, Telnet hardening, AAA login authentication, and IOS XE device administration.