Which one means of transport is unidirectional?

The correct answer is Option (1) → Pipelines

Pipelines are a unidirectional means of transport. They are designed to transport goods, typically liquids or gases, in one direction. Pipelines are commonly used for the transportation of products like oil, natural gas, and liquids, and once they are set up, the flow is typically in one direction from the source to the destination. Other modes of transport such as roads, railways, or air transport, pipelines allow bi-directional movement.