How did the development of a surplus in primitive agricultural society allow for occupational specialization and possible social stratification?

A vert short answer is: people had time. 

Before this, people were focused on not starving and everyone's attention was turned to gathering food. Noone could afford doing anything else than gathering food for themselves (and maybe their offspring) because then they would starve. But, with the surplus of food, some people could focus on innovations and those innovations (such as writing) gave them a higher status, which ultimately led to a stratification. 

While winters are rainy, summers are dry. regions with this climate are usually in the eastern part of the continents. they experience hot, humid summers and colder winters. precipitations have a regular distribution throughout the year, but hurricanes are common.

The answer is b or dmost likely bhope it