What Is the Purpose of Noting "C: Alice Adams, M

What is the purpose of noting "c: Alice Adams, M.D." at the bottom of a letter?

A) To request that the receiver make a copy of the letter for Dr. Adams
B) To instruct the medical assistant to send the same letter to Dr. Adams
C) To advise the receiver that a duplicate letter has been sent to Dr. Adams
D) To tell the receiver that Dr. Adams has more information about the subject of the letter