The question is asking us to determine the region where moved the Khmer and Mon peoples from 800 to 1200. The Khmers are very old ethnic group that came into Southeast Asia at the same time as the Mon people. They were builders of the Khmer Empire in Cambodia ( 802 - 1431 ). Answer: They moved into the northern regions of A ) Cambodia.
Between 800 and 1200 CE, the Khmer and Mon peoples primarily moved into the northern regions of Cambodia, where they played a significant role in establishing and developing the Khmer Empire. This migration was driven by the search for land and the establishment of cultural and economic opportunities. Therefore, the correct answer is A) Cambodia.
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