Which of the following is NOT a method of terminating actual authority?

In the context of agency law, actual authority can be terminated through several means, but the options listed are differentiated by their nature regarding actual authority.

The correct choice indicates that injury to the agent does not constitute a recognized method for terminating actual authority. Actual authority is a defined power granted to an agent to act on behalf of the principal, which can more properly be terminated by specific legal events or actions.

When considering the other options, death of the principal or agent constitutes a definitive termination of authority because the fundamental relationship is no longer valid; authority ceases to exist. Similarly, unilateral cancellation by the principal is a direct exercise of control over the agency relationship, allowing the principal to revoke the agent's authority at will. Finally, mental incapacity of the principal or agent creates a situation where the necessary capacity to enter into and fulfill the terms of an agency relationship is impaired, thereby terminating actual authority.

In conclusion, injury to the agent does not inherently affect the ability of that agent to act on behalf of the principal and thus does not serve as a means of terminating actual authority.