**Core Concept**
Obsessive-compulsive disorder (OCD) is a psychiatric condition characterized by recurrent, intrusive thoughts (obsessions) and repetitive behaviors (compulsions) that an individual feels compelled to perform. The pathophysiology of OCD is believed to involve abnormalities in the cortico-striatal-thalamo-cortical (CSTC) circuit, particularly involving serotonin (5-HT) neurotransmission.

**Why the Correct Answer is Right**
The correct answer is related to the effectiveness of a specific medication class in treating OCD symptoms. Selective serotonin reuptake inhibitors (SSRIs) are the first-line treatment for OCD, as they increase the levels of serotonin in the synaptic cleft, thereby reducing the symptoms of the disorder. This is achieved through the blockade of the serotonin transporter (SERT) protein, which is responsible for the reuptake of serotonin from the synaptic cleft.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the primary mechanism of action of SSRIs in OCD treatment.
**Option B:** This option is incorrect because it implies that the primary treatment for OCD is pharmacological, when in fact, a combination of pharmacological and psychological interventions (such as cognitive-behavioral therapy) is often used.
**Option C:** This option is incorrect because it does not accurately describe the pathophysiology of OCD, which involves abnormalities in the CSTC circuit and serotonin neurotransmission.

**Clinical Pearl / High-Yield Fact**
SSRIs are effective in reducing the symptoms of OCD because they increase the levels of serotonin in the synaptic cleft, thereby reducing the excitability of the CSTC circuit and decreasing the frequency and intensity of obsessive thoughts and compulsive behaviors.

**Correct Answer:** B. SSRIs are the first-line treatment for OCD.