Explanation:

- Observation: Management principles are often derived from observing real-world business operations and understanding patterns and repeated behaviors.

- Experimentation: Trial and error, along with structured experiments, help refine management practices, leading to well-tested principles.

- Personal experiences of the manager: Managers learn from their own direct experiences in the workplace, applying lessons learned to develop practical management principles.

- All of the above: Management principles encompass a broad range of inputs, including observation, experimentation, and personal experiences. Together, these sources create a comprehensive understanding of effective management.