Concept:Ultra vires is a Latin term used in administrative law to describe action that goes beyond legal authority.
Explanation:A public authority is given powers by its enabling law or the Executive.
When the authority acts within those powers, its actions are valid.
However, if it acts outside the scope of its statutory duties, such action is described as ultra vires.
The phrase literally means "beyond the powers".
Therefore, ultra vires refers to an act that exceeds the legal limits of the authority concerned.
Answer:C. a situation where a public authority acts beyond the scope of its duties.