Final answer:
The concept of human equality led to revolutions in political and social structures, but it failed in economic reforms. Option a.
Step-by-step explanation:
The concept of human equality led to revolutions in political and social structures, but it failed in economic reforms. The Enlightenment ideas of human equality and individual rights greatly influenced the French Revolution and the American Revolution. These revolutions aimed to overthrow oppressive systems, establish democratic governments, and ensure equal rights for all citizens. However, while these revolutions brought significant changes in political and social systems, they often failed to address economic inequality and implement substantial economic reforms.