Answer:
A. decreased trade with outside societies
Step-by-step explanation:
Agricultural yield is defined as the amount of production per unit area. Production are either in the food crops or cash crops, if the food crops or cash crops yields are increased, the settlements are established around the region because opportunity of income diversified and more. The population size is an increasing trend and labours are diversified, people get the sophisticated life and livelihood must be upgraded. Then they innovate the new technology in agriculture sector and it yields more than before, the region became self reliance in nature, they will export the surplus production via trade.