Horney's actual research approach relied mainly on

A) studies exclusively using twins reared apart.
B) correlational research involving self-report inventories.
C) case studies.
D) observations of students within a classroom setting.

Horney's research approach mainly relied on case studies, as she believed that understanding individual experiences and behaviors was crucial to understanding personality development. She used psychoanalytic techniques such as free association and dream analysis to gather data for her case studies.