The correct answer to this open question is the following.
Although there are no options attached we can say the following.
The reasons for the expansion of human life to different parts of the world in the Neolithic age were basically the following.
The Neolithic was a turning point in the history of humanity. Humans stopped being nomads and started to settle in one place. They learned agriculture techniques and started to grow crops to feed their families instead of following the herds to hunt animals. Humans also started to domesticate animals.
Many historians identify this time as the Neolithic Revolution. And an important factor that contributed to this was the warning of the earth's climate.
Humans started to settle in one place as was the case of the Sumerians in the Middle East, between the Tigris and Euphrates Rivers, where they established powerful city-states such as Kish, Ur, Lagash, Uruk, Nippur, or Eridu.
Ancient Egyptians settled on the banks of the Nile River. The Harappan or Indus Valley civilization did the same next to the Indus Valley in India. And ancient Chinese people settled next to the Yellow River, in China.
