What type of track is necessary for loading or unloading tank cars?

The correct choice is focused on the operational requirements for loading or unloading tank cars, which is best accommodated by a spur track or bypass line. This type of track is typically a short, auxiliary track that branches off from a main track.

A spur track is specifically designed to provide direct access to industrial sites, including facilities where tank cars are loaded or unloaded. This design allows for safe and efficient transfer of materials, such as petroleum products, without interfering with the mainline train operations. The configuration of spur tracks can accommodate the specific needs of tank cars, such as the space and maneuverability required to handle the loading equipment and ensure safety during operations.

In contrast, options like single-track only, high-speed rail lines, and circular tracks do not meet the logistical and safety requirements necessary for the effective operation of loading and unloading tank cars. Single-track setups may limit the space needed for handling tank cars, high-speed rail lines are not designed for stop-and-load operations, and circular tracks do not provide the necessary direct access to loading points.