The best answer is B. The passage states that “Native Americans recognized that the essence of their lives could not be communicated in English,” that is, in the language of the ethnologists recording the life stories. Since this statement supports the idea that “much was inevitably lost,” it can be inferred that the informants used a language other than that used to record their life stories. Choice A is incorrect because, in the second paragraph, the investigators are criticized for lacking familiarity with the cultures they study. Choice C is incorrect because ethnologists recorded life stories to “supplement their own field observations”. Choice D is incorrect because the passage indicates that life stories were edited.