What command is used to configure the encapsulation type on a trunk port?

The command used to configure the encapsulation type on a trunk port is structured to allow the specification of the encapsulation method that will be used on the trunk. In this case, the correct option utilizes the pattern where "encapsulation-type" refers to the actual encapsulation method being set, such as ISL (Inter-Switch Link) or 802.1Q. The command is designed to be clear about the requirement to indicate the type of encapsulation expected on the trunk.

Configuring a trunk port correctly is essential for ensuring that VLAN traffic can traverse between switches and that the frames maintain their VLAN information as they pass through the network. The encapsulation type determines how this information is included in the Ethernet frame, making it a crucial setting for proper VLAN operation.

The other choices do not follow the correct syntax or command structure recognized in Cisco IOS commands for configuring trunk encapsulation, making them ineffective. Each of these alternatives either misrepresents the required terminology or lacks the necessary context for setting the encapsulation type.