A very high-speed data transmission line that provides networking facilities to relatively small but high-speed internet service providers all around the world is known as

A backbone is a very high-speed transmission line that links smaller high-speed ISPs across the world.

A pathway is a vague term and not the name for this high-capacity trunk line.

A communication system is a broad phrase, not the specific high-speed backbone.

Routers are devices that forward packets, not the transmission line itself.

Backbones carry the bulk of long-distance internet traffic between regions.

Undersea fibre-optic cables form much of the global internet backbone.