**Core Concept:** "Psychosexual Development" is a theory in psychology that describes the psychological and sexual development of humans during various stages of life. The theory is related to the stages of human sexual development proposed by Sigmund Freud, a pioneering psychoanalyst.

**Why the Correct Answer is Right:** Carl Gustav Jung, a Swiss psychiatrist and psychoanalyst, is the correct answer. He developed the theory of psychosexual development, which is based on Freud's work. Jung's theory focuses on the individual's psychological development, exploring their experiences, fantasies, and dreams.

**Why Each Wrong Option is Incorrect:**

A. Sigmund Freud: While Freud is the father of psychoanalysis, he formulated the theory itself, not Carl Jung.

B. Ernest Jones: Ernest Jones was a British psychiatrist and biographer who studied and promoted Freud's work, but not Jung's theory.

C. Wilhelm Reich: Wilhelm Reich was a German psychoanalyst who focused on the body-mind relationship but contributed to a different area of psychoanalysis.

D. Karen Horney: Karen Horney was a German-American psychoanalyst who focused on the interplay between personality traits and social influences, but not on psychosexual development.

**Clinical Pearl / High-Yield Fact:** Understanding the theories of psychosexual development, particularly Freud's and Jung's, is essential for medical students, psychiatrists, and psychologists. These theories provide insights into human behavior, personality, and sexual development, helping to diagnose and treat mental health disorders and provide context for understanding human psyche.