What term refers to the role of the Vice-President if the President is unable to serve?

The correct term that refers to the role of the Vice-President if the President is unable to serve is "Succession." In the context of U.S. government, succession is the established protocol for determining the next in line for the presidency. The Vice-President is specifically designated as the first in line to assume the presidency in the event that the President is incapacitated, resigns, dies, or is removed from office. This ensures continuity and stability in leadership within the executive branch.

The other terms do not accurately capture this constitutional concept. An administrative role generally refers to the duties and responsibilities assigned to an individual in a management position and does not denote a process of filling the presidential role. Interim executive might imply a temporary leadership situation, but it does not reflect the specific constitutional provision for the Vice-President. Similarly, the term "stand-in President" is not official terminology in this context and lacks the formal recognition associated with presidential succession outlined in the U.S. Constitution.