According to the passage, collecting life stories can be a useful methodology because:
Life stories provide deeper insights into a culture than the hypothesizing of academics that are not members of that culture
The author very clearly states in the first paragraph that “Ethnologists had a distinct reason for wanting to hear the life stories: they were after linguistic or anthropological data that would supplement their own field observations, and they believed that the personal stories, even of a single individual, could increase their understanding of the cultures that they had been observing from without.” Answer option (a) restates the same thing. In fact, answer options (b), (c) and (d) have not been mentioned by the author in the passage at all as a reason as to why collecting life stories can be a useful methodology. Hence, it is evident as answer option (a) is the correct answer choice.