Which parameter in the netstat command displays all active TCP connections as well as the TCP and UDP ports on which the computer is listening?

The parameter that displays all active TCP connections as well as the TCP and UDP ports on which the computer is listening is the one that includes the functionality to show all connections and listening ports. The correct choice, which is indeed the one specified, allows users to see a comprehensive list of all network connections and listening services.

The "-a" option in the netstat command provides a complete overview of all connections and listening ports, giving crucial insights into network activity. This is particularly valuable in digital forensics and network troubleshooting, as it allows forensic analysts to identify any potentially malicious connections or unauthorized listening services on a system.

The other options provide different functionalities: "-n" displays addresses and port numbers in numerical form without resolving them to hostnames, "-p" shows the process associated with each connection, and "-o" includes the owning process ID for each connection. While these options offer various useful details, only the specified option provides the comprehensive overview of both active connections and listening ports.