**Core Concept**
The treatment of **Obsessive Compulsive Disorder (OCD)** involves the use of medications that can modulate **serotonin** levels in the brain, as **serotonin** imbalance is a key factor in the pathophysiology of OCD. **Selective Serotonin Reuptake Inhibitors (SSRIs)** are commonly used.

**Why the Correct Answer is Right**
Although the exact options are not provided, typically, **SSRIs** such as fluoxetine, sertraline, and paroxetine are used in the treatment of OCD. These drugs work by inhibiting the reuptake of **serotonin** in the synaptic cleft, thus increasing the availability of **serotonin** for neurotransmission.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option, it's challenging to provide a precise reason, but generally, any option that is not an **SSRI** or **clomipramine** (a tricyclic antidepressant with serotonin reuptake inhibiting properties) would be incorrect.
**Option B:** Similarly, without specifics, any drug not primarily affecting **serotonin** levels or not used in OCD treatment would be wrong.
**Option C:** and **Option D:** would follow the same logic as Options A and B.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **SSRIs** are the first-line treatment for OCD due to their efficacy and relatively favorable side effect profile compared to other antidepressants.

**Correct Answer:** Correct Answer: D. SSRIs.