Why would the early americas be considered diverse or complex

They were made up of the colonies. New England colonies were very conservative, not religiously tolerant, and a similar minded community. They banished a few people who threatened their community like Anne Hutchinson. The Chesapeake colonies were the most diverse and accepting because they were in between the Southern colonies and New England colonies. The Southern colonies were primarily made up of the slave population, which of course brought out the racist thoughts in the Caucasian people of the South. 

The answer to your question would be b