Answer:
c) participant-observers
Step-by-step explanation:
-Third-party observer is an additional person that is involved in the assesment.
-Actors refer to people tha perform a character.
-Participant-observer is when researchers are allowed to learn about what is being studied by participating in the activities that are part of the research.
-Active researchers refers to practitioners that are part of a company that perform the research in their area to help fix a problem.
-Imitators refer to people that copy other people's actions.
According to this, the answer is that in this example, researchers are participant-observers are researchers are placed in the stores s sales people.