Is a cargo tank always permanently attached to a motor vehicle?

A cargo tank is not always permanently attached to a motor vehicle, which is why the correct choice is that it is not necessarily so. Cargo tanks can be designed to be either permanently mounted or removable, depending on the vehicle's design and the intended use. For example, some tanks are built as part of the vehicle's chassis, facilitating permanent attachment for specific transporting tasks, while others can be detached and moved independently or switched between different vehicles.

This flexibility allows for various configurations based on the needs of transporting hazardous materials. It's important to understand that the nature of the cargo tank's attachment has implications for loading, unloading, and safety regulations, highlighting the necessity of adhering to specific guidelines regardless of the tank's attachment status.

Other choices imply limitations or conditions that would not accurately reflect the various designs and operational scenarios that exist within the transportation of hazardous materials.