Which of the Following Is a Difference Between Observation and Ethnography

Which of the following is a difference between observation and ethnography?

A) Ethnography involves taking detailed field notes, while observation does not.
B) Observers always remain very detached from the people they are observing, but ethnographers do not.
C) Ethnography requires deep, daily immersion for months or years, while observation takes much less time.
D) Observation research involves studying group norms, while ethnography does not.