As part of a tenth-grade Social Living course, a teacher has a guest speaker come to his classroom ...

As part of a tenth-grade Social Living course, a teacher has a guest speaker come to his classroom to talk about the dangers of drug use. The guest speaker is a former drug dealer and hardcore drug user, who became involved in crime as a result of his connection to drugs, spent many years in jail, later entered a drug rehabilitation program, and finally cleaned up his act. Social psychologists would refer to this kind of communicator as a(n) ____.
 
  a. sleeper source
  b. convert communicator
  c. normative communicator
  d. implicit source