Why Is Participant Observation Considered Especially Important to Ethnographic Research

Why is participant observation considered especially important to ethnographic research?

A) The anthropologist will have personal experience with the habits and customs of the people being studied.
B) It protects the anthropologist from appearing foolish while gathering information about a culture.
C) It provides the anthropologist with valuable insights into the culture without having to know its language.
D) The people being studied will be unable to keep information a secret from the ethnographer who is living with them and is therefore a part of their culture.