Correct answer:
3) The Crusades led to a money-based system of exchange.
In addition to the fighting that went on as the main "business" of the Crusades, there was also plenty of economic business that happened too. Various goods were brought back to Europe from the regions in the Middle East where the Crusaders traveled. Food items (such as coffee and rice) and other items (such as carpets and compasses) were obtained by Europeans from Muslim traders. Trade networks were established, and a regulated currency system was developed to facilitate fair trade between Europe and the Middle East.