The Correct Stance or Attitude for a Survey Research Interviewer

The correct stance or attitude for a survey research interviewer to take is

A) as an actor or actress told to read lines without any facial expression or any change in tone of voice, like a robot.
B) an aggressive police interrogator.
C) a neutral tone, with natural expression of the exact wording on the interview schedule.
D) a close friend, therapist, or family member.
E) an expressive, interested participant to the point of beginning arguments on issues.