The time prior to the use of written records.
Answer:
i believe its B sorry if im wrong
Explanation:
The Great Wall of China, built more than 2,000 years ago, stands as one of the monumental feats of ancient engineering. But before the Great Wall, warring Chinese dynasties built many other walls for protection. There are 7,000 watchtowers, blockhouses for soldiers, and beacons to send smoke signals. Nineteen walls have been built that were called the Great Wall of China. The first was built in the 7th century BC.
D is the answer Hope it helps
If the question is asking you all except which, the answer is "people fled the urban centers because they had become too crowded and unsanitary"
