**Core Concept**
Agranulocytosis is a potentially life-threatening condition characterized by a severe deficiency of granulocytes, a type of white blood cell crucial for fighting infections. Certain medications, including some antipsychotics, can cause agranulocytosis as a rare but serious side effect.

**Why the Correct Answer is Right**
Clozapine is an atypical antipsychotic primarily used for treatment-resistant schizophrenia. It has a well-documented risk of inducing agranulocytosis, necessitating regular blood monitoring in patients receiving this medication. Clozapine works by blocking dopamine D2 receptors and serotonin 5-HT2A receptors, although its exact mechanism of agranulocytosis is not fully understood. Regular monitoring of white blood cell counts is essential when prescribing clozapine to prevent this potentially fatal side effect.

**Why Each Wrong Option is Incorrect**
**Option A:** Haloperidol is a typical antipsychotic that can cause extrapyramidal side effects but does not have a significant risk of agranulocytosis. Haloperidol primarily blocks dopamine D2 receptors without the same risk profile as clozapine.

**Option B:** Olanzapine is another atypical antipsychotic that is not typically associated with agranulocytosis. While it can cause various side effects, including weight gain and metabolic changes, agranulocytosis is not a common concern with olanzapine.

**Option C:** Risperidone is also an atypical antipsychotic with a lower risk of agranulocytosis compared to clozapine. It is used for treating schizophrenia and bipolar disorder but does not carry the same warning for agranulocytosis as clozapine.

**Clinical Pearl / High-Yield Fact**
Regular monitoring of white blood cell counts is essential when prescribing clozapine to prevent agranulocytosis. This includes weekly monitoring for the first six months, then bi-weekly for the next six months, and monthly thereafter.

**Correct Answer:** C.