Answer:
Option D.
Step-by-step explanation:
With the migration of people from fertile areas, knowledge of agriculture spread by diffusion. The term migration is defined as the movement of people from their original area to a new one for living purposes. Diffusion is defined as the act of spreading something in a wider spectrum. In summary, the phrase means that when people who historically lived in rural fertile areas moved to different places, they started to spread around their knowledge of agriculture.