**Core Concept**
Obsessive compulsive disorder (OCD) is a mental health condition characterized by recurring, intrusive thoughts (obsessions) that trigger repetitive behaviors or mental acts (compulsions) aimed at reducing anxiety and preventing perceived harm or contamination.

**Why the Correct Answer is Right**
The correct answer encompasses the major symptoms of OCD, which include contamination fears, pathological doubts, and intrusive thoughts. Contamination fears involve excessive worries about germs, dirt, or other substances that may cause harm, leading to compulsions to clean or avoid certain situations. Pathological doubts involve persistent doubts about whether one has performed a task correctly, such as locking doors or turning off appliances, leading to compulsions to check and re-check. Intrusive thoughts are unwanted, distressing ideas, images, or urges that invade a person's mind, often leading to compulsions to neutralize or prevent them. The combination of these symptoms is characteristic of OCD.

**Why Each Wrong Option is Incorrect**
**Option A:** While contamination fears are a common symptom of OCD, they are not the only symptom, making this answer incomplete.
**Option B:** Pathological doubts are a symptom of OCD, but excluding other symptoms like contamination fears and intrusive thoughts is incorrect.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that intrusive thoughts in OCD are not necessarily the content of the thought itself, but rather the distress and anxiety they provoke. This distinction is crucial in differentiating OCD from other mental health conditions.

**✓ Correct Answer: D. All the above**