Final answer:
The principle that dictates a subordinate should have only one supervisor is known as Unity of Command, which is part of an organization's chain of command.
Step-by-step explanation:
The principle that states that a subordinate has only one supervisor to whom he or she is directly responsible is called Unity of Command. This principle ensures clarity and accountability within an organization's hierarchy of authority. As seen in the example of a Walmart employee, the shift manager is in charge of store employees and similarly is responsible to the store manager, who then answers to the regional manager, and so on, forming a chain of command that ultimately leads to the CEO, the board members, and the stockholders.