As we do not have access to this text, we cannot provide examples, citations or references of this text. However, we are able to look at what servant leadership is and how it is exercised in the world.
Servant leadership is a philosophy of leadership in which a person is considered a leader because he serves. This kind of leader puts the needs of his employees first. Moreover, his main focus is that of helping the employees thrive and develop as much as possible. According to this philosophy, instead of the people working to serve the leader, the leader exists to serve the people.
I believe it is B because for a monopoly it has no close substitute and is protected by a barrier that prevents other firms from selling that good or service