Referent power is gained by a leader who has strong interpersonal relationship skills.
A person who has strong referent power is usually a leader who has great charismatic traits and strives to make others feel comfortable and happy.\ in his/her presence.
I would say that A is the answer. B is irrelevant, C makes the point debatable as it acknowledges that not everyone has access and I feel like A is more important than D to the sort of people who would set questions