What was the main causes of the French Revolution

The main causes of the French Revolution was the growing popularity of the works of a number of intellectuals who argued for social reform.
Crop failures in 1788 compounded existing economic restlessness.
French participation in the American Revolution that drove the government to the brink of bankruptcy.
Resentment among the bourgeoisie about being excluded from political power
The French monarchy, no longer seen as divinely ordained, was unable to adapt to the political and societal pressures being exerted on it.
Widespread inequality between the rich and poor classes alongside growing dissatisfaction with the antiquated feudal system among the poor.

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The answer would be political systems .