Explanation:

- Option 1: An agency can be terminated if the principal revokes the authority granted to the agent. This revocation must be communicated, and in some cases, it may need to be justified to avoid liability.

- Option 2: Similarly, the agency ends if the agent decides to renounce the business of the agency. The agent should ideally inform the principal and handle any pending obligations.

- Option 3: The death or insanity of either the principal or the agent automatically terminates the agency because the agent's role hinges on the direction and control of the principal.

- Option 4: All the above - All these scenarios: revocation by the principal, renunciation by the agent, or the death or unsound mind of either party, lead to the termination of an agency.

Correct Answer: Option 4 - All the above