I believe the correct answer is: its emphasis on planned efforts focusing on people and their interrelationships in organizations
Organizational development (OD) represents a system wide application of behavioral science knowledge which primary goal is to develop, improve and reinforce the strategies, structures and processes that will lead to organizational effectiveness in future.
Therefore, the essence of an organizational development (OD) approach to change is its emphasis on planned efforts focusing on people and their interrelationships in organizations.