I would say B because a surplus of food means that there is a lot of food to go around, meaning that people wouldn't have to worry about finding food all the time. So, they could go specialize in other jobs and skills, leading away from a food-centered civilization
Japan is m up for several islands
During times of civic unrest such as riots, the national government can summon the national guard to its help if it thinks that the local forces cannot stop it or if the riots are going out of hand.
One would be the opening of oceans and rivers allowed them to ship what they made to other places and also receive materials needed in their processes.