Explanation: Use POE on this question. Choice (A) describes a technique used by settled groups who began to practice agriculture, a key element of Neolithic humans, so get rid of (A). The Neolithic Era was also known as the Bronze Age, as humans figured out how to combine metals; eliminate (B). Choice (C) is another true statement: The settling of groups led to the creation of land borders and, therefore, conflicts over those borders. Choice (D) is the answer.