Read this and answer the question. If the question is unanswerable, say "unanswerable".

Since the work of Franz Boas and Bronisław Malinowski in the late 19th and early 20th centuries, social anthropology in Great Britain and cultural anthropology in the US have been distinguished from other social sciences by its emphasis on cross-cultural comparisons, long-term in-depth examination of context, and the importance it places on participant-observation or experiential immersion in the area of research. Cultural anthropology in particular has emphasized cultural relativism, holism, and the use of findings to frame cultural critiques. This has been particularly prominent in the United States, from Boas' arguments against 19th-century racial ideology, through Margaret Mead's advocacy for gender equality and sexual liberation, to current criticisms of post-colonial oppression and promotion of multiculturalism. Ethnography is one of its primary research designs as well as the text that is generated from anthropological fieldwork.

When did Bronislaw Malinoswki and Franz Boas do their relevant work?
late 19th and early 20th centuries