The mongol conquests of much of Eurasia in the thirteenth century tended to encourage trade along the silk roads primarily by
A) opening large new markets for both european and east asian goods in central asia
B)increasing the demand or military supplies needed by the mongol armies that occupied various regions
C)decreasing the risk of bandit attacks and reducing the number of local rulers collecting tribute from trade caravans
D)discouraging seaborne trade along the Indian Ocean routes that competed with the silk roads