As a service provider you must support a Layer 2 virtualization protocol that does not include the use of label switching. Which option can meet this design requirement?

VPLS (Virtual Private LAN Service) is a Layer 2 VPN technology that relies on MPLS label switching to transport Ethernet frames across a provider network, violating the no-label-switching requirement.

VRF-Lite is a Layer 3 virtualization technique that creates separate routing instances on a single device without MPLS, but it is not a Layer 2 virtualization or tunneling protocol.

QinQ, also known as IEEE 802.1ad or dot1q-in-dot1q tunneling, encapsulates customer 802.1Q frames within a service provider VLAN tag to create Layer 2 tunnels across a provider network. It operates purely at Layer 2 using double VLAN tagging and requires no MPLS infrastructure or label switching, satisfying the design constraint.

802.3ad (now IEEE 802.1AX) defines Link Aggregation Control Protocol (LACP) for bonding multiple physical links, not a Layer 2 virtualization or tunneling protocol.