Refer to the exhibit.

The correct response is C. The trunk must add the missing VLAN to the allowed VLAN list without removing existing working VLANs. The command to add VLAN 13 preserves the current allowed VLANs and enables communication to the file server. For Cisco CCNA 200-301 v1.1, the important point is the mechanism, not a generic description of the technology. Replacing the allowed list with only one VLAN or removing existing VLANs would interrupt other communications. When this appears in a network, the symptom normally confirms the answer: the route installed, the state selected, the packet forwarded, the wireless client behaviour, or the management workflow will follow this rule. That is why this answer is the best fit for the scenario and not just a plausible networking term.