How does the author create an analogy between the People living in peace with the Black Robes and trading corn seeds for watermelon seeds?

In this selection, the author creates an analogy between the People living in peace with the Black Robes and
A trading corn seeds for watermelon seeds.
B the religion and language of a group of people.
C growing corn and watermelon together.
D the sun and the water that feed the crops.