You have configured a new VLAN 9 and applied it to the interface. However, you find that the computer still remains in VLAN 1. What is the problem? Refer to the following exhibit.

A. The switchport is configured with switchport nonegotiate.
B. The switchport is configured as a trunk and dot1q trunking is intervening.
C. The switchport is configured as a trunk and the native VLAN is VLAN 1.
D. Spanning-tree PortFast is configured and defaulting to VLAN 1.

C. The switchport is configured as a trunk, but since the computer was originally in VLAN 1 and the native VLAN of the interface is VLAN 1 by default, all traffic untagged was directed to the native VLAN.