## Core Concept
Obsessive-Compulsive Disorder (OCD) is an anxiety disorder characterized by recurrent, intrusive thoughts (obsessions) and repetitive behaviors (compulsions). The comorbidity of OCD with personality disorders is a significant area of study. Among personality disorders, one type has a particularly close association with OCD.

## Why the Correct Answer is Right
The correct answer, **Anankastic Personality Disorder (also known as Obsessive-Compulsive Personality Disorder)**, shares many features with OCD. Both conditions involve a preoccupation with orderliness, perfectionism, and mental and interpersonal control. Individuals with Anankastic Personality Disorder are characterized by their excessive orderliness, perfectionism, and control, which are similar to the compulsive behaviors seen in OCD. The similarity in symptomatology and the shared underlying psychological mechanisms, such as a high need for control and difficulties with flexibility, contribute to the association between OCD and Anankastic Personality Disorder.

## Why Each Wrong Option is Incorrect
- **Option A:** While individuals with OCD may exhibit avoidant behaviors, Avoidant Personality Disorder is primarily characterized by social inhibition, feelings of inadequacy, and hypersensitivity to criticism or rejection. It does not share the same core features with OCD.
- **Option B:** Borderline Personality Disorder is marked by instability in interpersonal relationships, self-image, and affects, and marked impulsivity. This does not directly correlate with the core symptoms of OCD.
- **Option C:** There is no commonly recognized personality disorder labeled simply as "C" in standard psychiatric classification systems like DSM or ICD.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that patients with OCD are at a higher risk of also having Anankastic Personality Disorder, and vice versa. This comorbidity can influence treatment approaches, with therapists sometimes needing to address both the OCD symptoms and the personality disorder traits.

## Correct Answer Line
**Correct Answer: D. Anankastic Personality Disorder.**