When connecting two Fibre Channel switches using different domain IDs, which of the following would be used?

An Inter-Switch Link (ISL) is used to connect two Fibre Channel switches, enabling them to discover each other, negotiate fabric parameters, and merge their fabrics into a single, cohesive entity despite having different domain IDs.

DSL (Digital Subscriber Line) is a technology for internet access over copper phone lines and is completely unrelated to Fibre Channel networking.

While ISLs can be trunked (multiple physical links bundled into a single logical ISL), 'trunking only' is an incomplete answer as it describes a feature applied to an ISL, not the fundamental link type itself.

A port channel, or link aggregation group, is a concept primarily used in Ethernet networks to bundle multiple physical links; the equivalent function for Fibre Channel switch-to-switch connectivity is achieved via ISLs, which can then be trunked.