Most of Arthur and Yousef's Friendship Involves Jogging Together and Simple

Most of Arthur and Yousef's friendship involves jogging together and simple chitchat over coffee, but one weekend Yousef tells Arthur about his mother's recent cancer diagnosis. Arthur and Yousef's relationship reflects which of the four principles of self-disclosure?

A) Self-disclosures occur between two people in a close relationship.
B) Self-disclosing is reciprocal.
C) We disclose a lot in a few encounters.
D) Self-disclosures occur gradually over time.