**Core Concept**
In psychoanalytic theory, obsessive-compulsive disorder (OCD) is linked to fixation during early childhood development, particularly the anal stage of psychosexual development. This stage occurs between ages 18 months and 3 years, where children learn toilet training, and unresolved conflicts about control, order, and cleanliness may lead to fixation.

**Why the Correct Answer is Right**
The anal stage is associated with the development of control, order, and cleanliness. Obsessive-compulsive behaviors—such as excessive cleaning, organizing, and ritualistic actions—are believed to stem from unresolved conflicts during this stage, particularly anxiety about loss of control or messiness. Freud proposed that failure to achieve successful toilet training leads to anal fixation, manifesting as compulsive behaviors in adulthood.

**Why Each Wrong Option is Incorrect**
Option A: The Oedipal stage (ages 3–6) involves unconscious desires for the opposite-sex parent and is linked to identity formation, not compulsive behaviors.
Option B: The genital stage (adolescence onward) involves mature sexual interest and interpersonal relationships, not fixation related to OCD.
Option C: The oral stage (birth to 18 months) is associated with issues like dependency, overeating, or smoking, not obsessive-compulsive tendencies.

**Clinical Pearl / High-Yield Fact**
Remember: **"Anal fixation = obsession with order, cleanliness, and control"** — a classic Freudian link, though modern psychiatry views OCD through cognitive-behavioral and neurobiological lenses, not psychoanalytic theory.

✓ Correct Answer: D. Anal stage