The correct answer is C. Communication.
Communication is the process of exchanging information, ideas, or feelings between two or more people. It can be done through a variety of means, including verbal, nonverbal, and written communication.
Planning is the process of developing a plan or course of action. It involves setting goals, identifying resources, and developing strategies to achieve those goals.
Organizing is the process of arranging things in a systematic way. It involves creating order and structure, and ensuring that everything is in its place.
Staffing is the process of hiring and managing employees. It involves finding qualified candidates, interviewing them, and making hiring decisions.
In the context of the question, the only option that describes the exchange of ideas, opinions, information, etc. between two or more persons is communication.