Answer:
A.
Step-by-step explanation:
The ancient Chinese civilization was protected from invasion and cultural diffusion because of the geographical isolation. The ancient Chinese civilization was isolated by desert from the north and west, and the Pacific Ocean to the east.
The settlements along the Huang He river were not affected by cultural diffusion because they were isolated by the Gobi desert to the north, which kept people from invading the land.
Therefore, option A is correct.