Which of the Following Is the Best Example of Participant

Which of the following is the best example of participant observation? A researcher

A) videotapes the kinds of complaints that shoppers make at a customer service desk.
B) goes through medical records to investigate physician's errors.
C) attends a meeting of Alcoholics Anonymous to observe how people respond to excuses.
D) uses automobile insurance records to record how drivers explain their accidents.
E) is rude to some people in line at a movie theater and polite to others,and observes how they react.