Final answer:
The aristocracy, or Second Estate, was responsible for most of France's debt due to their tax exemptions and lavish lifestyles. The clergy, or First Estate, also contributed by holding wealth and land with minimal taxes.
Step-by-step explanation:
The French social class responsible for most of France's pre-revolutionary debt was the aristocracy. The aristocracy, known as the Second Estate, was composed of nobles who controlled a vast amount of wealth and land but contributed little to the country's revenue due to their tax exemptions. Their extravagant lifestyle, coupled with the opulent spending by kings such as Louis XIV on projects like the Palace of Versailles, and financial aid towards the American Revolution, significantly added to the national debt. Meanwhile, the First Estate, consisting of the clergy, also held a significant amount of the land and wealth yet had very minimal taxation. These privileges ultimately placed the burden of taxation on the Third Estate, which represented the vast majority of the French population, including the burgeoning bourgeoisie, workers, and peasants, who possessed neither the wealth nor the political power of the other two estates.