Enlightenment thinkers used to study human nature and improve society.
a.
science and medicine
c.
reason and logic
b.
theory and thought
d.
none of the above

Reason and logic

a European intellectual movement of the late 17th and 18th centuries emphasizing reason and individualism rather than tradition. It was heavily influenced by 17th-century philosophers such as Descartes, Locke, and Newton, and its prominent exponents include Kant, Goethe, Voltaire, Rousseau, and Adam Smith. (-google)

It would be A they used science and medicine to study human nature

Because of prejudice