Final answer:
Option (c), The tension between French settlers and American Indians in the Louisiana Territory was mainly due to French attempts to trade with tribes at war with each other, disrupting delicate alliances.
Step-by-step explanation:
The factor that most contributed to growing tensions between the French settlers in the Louisiana Territory and the local American Indians was French attempts to trade with tribes that were at war with each other. The French, unlike their British counterparts, placed a high value on maintaining friendly relations with Native Americans due to their reliance on the fur trade.
However, alliances with certain tribes often led to hostilities with the enemies of those tribes. By attempting to trade with tribes in conflict, the French risked the delicate balance they had managed to achieve with the various Native American groups. The French efforts were not sustained due to the outcome of the Seven Years' War and the Treaty of Paris in 1763, which ended French colonial ambitions in North America and disrupted the existing French and Native alliances.