Final answer:
DOT regulations require the person handling hazardous materials in a cargo tank to be in close proximity, typically within sight or sound, to manage emergencies or operational issues.
Step-by-step explanation:
The regulations set by the United States Department of Transportation (DOT) specify that the person responsible for loading and unloading a cargo tank containing hazardous materials must remain within a certain distance of the tank. This requirement ensures the individual is immediately available to handle emergencies or operational issues. The actual distance specified by the DOT regulations is not provided in the question; however, it is generally understood that the person should be in close proximity, often within sight or sound of the tank.