Final answer:
The answer is a) Territories. Spain's main post-war concern was maintaining the security of its western territories following the French Indian War and the Treaty of Paris in 1763.
Step-by-step explanation:
One of Spain's biggest concerns at the end of the French Indian War was the long-term security of their territories in the west. Therefore, the correct answer to the student's question is a) Territories.
After the Treaty of Paris in 1763, which marked the end of the conflict, the European powers re-drew the map of North America.
Spain was given control over Louisiana but lost northern Florida. With the shifting balance of power, Spain became increasingly concerned about the borders of its territories and the trade routes essential for economic prosperity.
Issues such as disputes with the United States over the boundaries of New Spain and access to the Mississippi River for trade were particularly troublesome.
The end of the French Indian War and subsequent treaties exposed Spanish holdings to new security challenges, leading to efforts to preserve their status in the region.