Answer:
The Yellow River (Huang He River) is often called the cradle of Chinese civilization. With a length of 3,395 miles (5,464 km)
The North wanted to spread their the communism to the south, and The south didn't want to hear about it, and have a democratic government. So to prevent that, the south started getting prepared for war, against communism and won, so that's how it started.
To be honest I feel like it’s C because there was a lot of harsh in the environment and conditions