A. decreased trade with outside societies
Explanation:
The question ask what will cause increase in agricultural yields within the society.
From the option above
A growing population size will definitely increase agricultural yield because as population increase more agricultural yield is required to meet the demand of the growing population.
Increase technology and sophistication of settlement will definitely cause increase in agricultural yield because as mechanized way of farming is practiced the yield will definitely increase because of the ability of machines to do more work compare to humans. Generally, advancement in technology and sophistication of settlement will support better idea and approach to agricultural practice thereby increasing the yield.
The diversification of labor of causes more yield in agricultural products because it improves expertise . Division of labor makes the job easier as each person is confined to man a particular units the yield of agricultural products is bound to increase.
Decrease trade with outside societies does not cause increase in the agricultural yield because it means the marketability of the product have been decreased since limited trade is observed outside the society thereby only support low agricultural yield.