Trunk interfaces can send both tagged and untagged frames.

An IEEE 802.1Q trunk interface is designed to carry traffic for multiple VLANs between switches. It accomplishes this by adding a VLAN tag to frames. However, a trunk port is also configured with a Port VLAN ID (PVID), which is equivalent to the "native VLAN" concept. When a trunk port sends a frame belonging to the VLAN specified by its PVID, it sends the frame untagged. For all other VLANs permitted on the trunk, the port sends the frames with an 802.1Q tag. Therefore, a trunk interface can and does send both tagged and untagged frames simultaneously.

This is a True/False question. The statement is true, making option A the correct choice.

1. Huawei HCIA-Datacom V1.0 Training Material. (2020). Chapter: "VLAN Principles", Section: "Link Types". The documentation explains that a trunk port sends frames tagged for allowed VLANs but sends frames untagged for the VLAN matching its PVID.

2. Huawei VRP V800R012C00 Configuration Guide - Ethernet Switching. (2018). Section: "Configuring a Trunk Interface". The guide details the behavior of trunk ports, stating, "By default, the PVID of an interface is VLAN 1. A trunk interface sends frames from the PVID untagged." This confirms the capability to send both tagged (for other VLANs) and untagged (for the PVID) frames.