Based on the provided information about the characteristics of the two colonial regions during the late seventeenth century, the true statement is:
The Southern colonies supported the plantation production of cash crops because of a long growing season.
This statement accurately reflects the agricultural practices in the Southern colonies, which relied on the cultivation of cash crops like tobacco, rice, and indigo due to their favorable climatic conditions and longer growing seasons. The other statements do not accurately characterize the regions' development and economic focus.