Which of the following commands would you use to start configuring a trunk port on a switch?

To start configuring a trunk port on a switch, the first step is to enter the global configuration mode. The command to access this mode is "configure terminal." This mode allows you to make changes to the switch's configuration, including specifying interface settings for trunking.

Once in global configuration mode, you can then proceed to select a specific interface and configure various properties, such as enabling trunking or setting the trunk mode. This follows the logical order of configuration: you cannot configure an interface or set trunking parameters without first entering the global configuration mode.

The other options represent either commands that would be used after entering configuration mode or concepts rather than direct commands to access the configuration. "Enable trunking" and "set trunk mode" are not valid commands for Cisco switches. Instead, you would typically use commands like "switchport mode trunk" after entering interface configuration mode, which can only be performed after starting from global configuration mode.