An Automotive Garage Provides Taxi Rides to People Who Are

An automotive garage provides taxi rides to people who are having their cars repaired. To determine the quality of their service, the garage uses taxis operated by employees of the garage who are trained to record the number of specific gripes a rider makes about the garage. This is an example of

A) A focus group.
B) Depth interviewing.
C) Direct observation.
D) Undisguised observation.
E) Disguised observation.