There are three people: Allen, Burt and Chris. One of these three people is a spy, one is a knave, and one is a knight. The knight always tells the truth, the knave always lies, and the spy can either lie or tell the truth. Allen says: "Chris is a knave.” Burt says: "Allen is a knight.” Chris says: "I am the spy.” Who is the spy, who is the knave, and who is the knight?