Which of the following ports MUST be open on the firewall to allow remote desktop connection and remote assistance traffic through?

Port 21 is typically used for File Transfer Protocol (FTP) and is unrelated to Remote Desktop.

Port 443 is typically used for HTTPS (HTTP Secure) traffic, which is encrypted web traffic, not RDP.

Remote Desktop Protocol (RDP) uses TCP port 3389 by default to establish connections between a client and a server. Opening this port on the firewall is essential for allowing users to remotely access and control a computer or server via RDP.

Port 8080 is often used as an alternative HTTP port or for proxy servers, not for standard RDP connections.