Which countries are an option?
The main reason for the wall's construction had always been defense. Since China's first dynasty, the empire faced a near-constant threat of attack from the nomadic tribes to the north. This included those famed Mongols as well as lesser-known groups like the Xiongnu and the Göktürks.
Yes the moisture in the air is a part of the hydrosphere.
Answer: I think the answer is cold front
Explanation:
