Final answer:
The Third Estate, dissatisfied with the unequal political system and heavy taxation, formed the National Assembly in 1789 and took the Tennis Court Oath, paving the way for the French Revolution.
Step-by-step explanation:
In response to the frustration with the other two estates and the unfair taxation and political system, the Third Estate created the National Assembly in 1789. The Third Estate represented the majority of the French population but lacked power and privileges, enduring heavier tax burdens while the First and Second Estates enjoyed exemptions. Influenced by the Enlightenment ideals and a demand for greater political representation, they first declared themselves a separate assembly on June 17, 1789, and later took the Tennis Court Oath, vowing not to disband until a constitution was established.
The formation of the National Assembly and the taking of the Tennis Court Oath marked significant steps towards the events that would unfold into the French Revolution. These actions were a clear assertion of the Third Estate's rejection of the old feudal and monarchial system that benefited the first two estates, leading up to important revolutionary moments such as the storming of the Bastille and the widespread demand for economic reform and equality.