The correct answer is A. Margaret Mead.
Margaret Mead was an American anthropologist who is known for her work on the study of culture and social relationships. She is particularly famous for her research on the cultures of Samoa and Papua New Guinea, which helped to establish participant observation as a common anthropological research practice.
Participant observation is a method of research in which the anthropologist immerses themselves in the culture or society they are studying and observes the behavior, interactions, and social dynamics of the people. It involves actively participating in the daily activities of the community and engaging with the people in order to gain an in-depth understanding of their culture and beliefs.
Margaret Mead used participant observation as a key part of her research on the cultures of Samoa and Papua New Guinea. She spent many years living in these communities and participating in their daily activities in order to gain insights into their culture and beliefs. Her work helped to establish participant observation as an important and effective method for studying cultures and societies.