What has helped to make Turkey a prominent center of commerce?

The greatest advantage of Turkey is its geographical position, which allows Turkey to connect two continents - Asia and Europe. Center of trade is the city of Istanbul, the only city that lies on two continent.

Explanation:

Even during the Middle Ages this whole region was an important center of commerce. Silk Road even back then was passing through todays Turkey. In modern Turkey commerce is one of the main sources of income, as traders, craftsmen... from different regions are coming to Turkey to trade and share knowledge and experience. Turkey is the link between Europe and Asia.

answer d to the question

answer; european crusades;