How did the Chinese use existing defenses in building the Great Wall?

How did the Chinese use existing defenses in building the Great Wall?

To protect China from its enemies and invaders from the North, especially the Mongols. The Mongols were a tribal group that would regularly conduct raids into China. Despite the wall, the Mongols eventually conquered China. The Wall also kept Chinese citizens from leaving China.

mali had been a state inside of the ghanaian empire. after ghana fell because of invading forces and internal disputes, mali rose to greatness under the leadership of a legendary king named sundiata, the "lion king." the songhai empire, already weakened by internal political struggles, went into decline.

d.) continue to rise rapidly