The most direct contribution to the geographic expansion of Safavid trade during the period from 1450 to 1750, as indicated in the passage, is:
- Safavid exchanges with European trading post empires in Asia
This option points to the Safavid Empire engaging in trade with European trading post empires in Asia. Such exchanges would have allowed the Safavids to expand their trade networks, access new markets, and establish economic relationships with European powers. This interaction would have facilitated the flow of goods, ideas, and technologies between the Safavids and European traders, contributing significantly to the geographic expansion of Safavid trade during this period.