What was a major reason for social inequality under the Old Regime?

Birth-based privileges

The governing concept is the estate-based social order of pre-revolutionary France. Under the Old Regime, social position and many rights were largely determined by birth. Members of the First Estate, mainly the clergy, and the Second Estate, mainly the nobility, enjoyed important privileges, including exemptions or advantages in taxation and access to high offices. Most people belonged to the Third Estate and carried many obligations without receiving equal political or social privileges. Therefore, birth-based privileges created a legally unequal society and helped produce resentment that contributed to the French Revolution. Equal opportunity, equality of taxes, and government by the people describe reform ideals, not the actual cause of inequality.

This is a Class 9 History question. Chapter: The French Revolution. Topic: French Society During the Late Eighteenth Century.