**Core Concept**
Atypical antipsychotics are a class of medications used to treat various psychiatric conditions, including schizophrenia and bipolar disorder. These medications have different side effect profiles due to their unique pharmacological properties. Sedation is a common adverse effect associated with some atypical antipsychotics.

**Why the Correct Answer is Right**
Sedation is most commonly associated with **Olanzapine (C)**, an atypical antipsychotic that acts as a potent antagonist of serotonin (5-HT2A) and dopamine (D2) receptors. The blockade of these receptors in the central nervous system contributes to its sedative effects. Additionally, olanzapine has a relatively high affinity for histamine H1 receptors, which can also contribute to sedation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Quetiapine is another atypical antipsychotic, but it is not the most sedating. It has a sedative effect due to its affinity for histamine H1 receptors but is not the most sedating among atypical antipsychotics.
* **Option B:** Risperidone is an atypical antipsychotic with a lower propensity for sedation compared to olanzapine. It has a higher affinity for dopamine D2 receptors, which may contribute to its higher incidence of extrapyramidal side effects.
* **Option D:** Ziprasidone is an atypical antipsychotic with a lower risk of sedation. It has a unique pharmacological profile with a lower affinity for histamine H1 receptors and a higher affinity for serotonin 5-HT1A receptors.

**Clinical Pearl / High-Yield Fact**
Atypical antipsychotics with a higher affinity for histamine H1 receptors (such as olanzapine and quetiapine) tend to have a higher risk of sedation. This is an important consideration when selecting an atypical antipsychotic for patients who may be at risk for sedation, such as the elderly or those with a history of substance abuse.

**Correct Answer:** C. Olanzapine is associated with the most sedation among atypical antipsychotics.