Answer:
Through interaction between traders and the locals along the trade routes.
Explanation
During their trades operation, a lot of interaction happened between the traders and the local people. During those interaction, they started to learn about each other's religion, culture, scientific development in their hometown , etc.
This is where the locals learn about the religion of the traders. After the traders left, the locals will spread the knowledge about that religion to other locals and contributed to the increasing amount of followers of that religion.
I agree with the person above - Athens has laws that treat all people fairly, regardless of social class.
Athens is the land of democracy, which supposedly means that people are equal and treated equally, not taking into account which class they belong to. Having this in mind, A is definitely incorrect; C is incorrect because all Greek city-states did that - Athens is no different; D is incorrect because every city-state had its constitution.
