Explanation
The technique that would fulfill the requirement of transferring data in multiple networks is 802.1Q tagging.
802.1Q tagging is a method of adding a tag or identifier to Ethernet frames that indicate which VLAN (Virtual Local Area Network) they belong to. VLANs are logical subdivisions of a network that allow devices in different physical locations or segments to communicate as if they were in the same network. VLANs improve network performance, security, and management by reducing broadcast traffic, isolating sensitive data, and grouping devices by function or department. By using 802.1Q tagging, two Layer 2 switches can exchange data from multiple VLANs over a single trunk link, without mixing or losing the VLAN information. References: CompTIA Network+ N10-008 Certification Study Guide, page 64; The Official CompTIA Network+ Student Guide (Exam N10-008), page 2-12.