In the context of the passage the highlighted sentence serves to A. explain the broader rationale for a conclusion described in the preceding sentence B. suggest some of the drawbacks of the riverbank location of the villages described in the following sentence C. acknowledge information that appears to undermine a description attributed to Orellana D. introduce a principle that appears to be contradicted by the agricultural development of premodern Amazonia E. give a reason for an upward revision in earlier estimates for premodern Amazonia