The Bash script is designed to loop through the available namespaces and output all registered interfaces within the Cisco NX-OS Guest Shell. The correct code snippet to complete the script is option C, ifconfig
"$ns". This command will display the network configuration for each namespace, allowing the engineer to view all registered interfaces.
References: The use of ifconfig in conjunction with namespace variables is a common practice in network scripting to retrieve interface information. For more detailed information on scripting in Cisco NX-OS, you can refer to the Cisco Nexus 9000 Series NX-OS Programmability Guide.