Which of the following is more commonly used for establishing high-speed backbones that interconnect smaller networks and can carry signals over significant distances?

Bluetooth is a short-range personal area network technology (typically under 100 meters) and is not designed for backbone or long-distance networking.

Ethernet is primarily a LAN technology and was not originally designed - nor is it the technology most commonly cited - as a backbone interconnect over significant distances compared to ATM in this context.

Token Ring is an obsolete IBM LAN technology operating at only 4 or 16 Mbps and is incapable of serving as a high-speed backbone for interconnecting networks over long distances.

ATM uses fixed 53-byte cells and supports speeds from OC-3 (155 Mbps) to OC-192 (10 Gbps), making it purpose-built for high-speed WAN backbones that interconnect LANs. It supports simultaneous voice, video, and data traffic with quality-of-service guarantees, which is why it was widely deployed in carrier-grade backbone infrastructure. Its cell-switching design minimizes latency and is well-suited for long-distance transmission.