**Core Concept**
Conivaptan is a non-selective vasopressin receptor antagonist used to treat euvolemic and hypervolemic hyponatremia. It acts by blocking the action of vasopressin (ADH) at the V1A and V2 receptors, leading to increased water excretion and correction of serum sodium levels.

**Why the Correct Answer is Right**
Conivaptan's dual action on V1A and V2 receptors is unique among vasopressin receptor antagonists. By blocking V1A receptors, conivaptan causes vasodilation and reduces peripheral resistance. By blocking V2 receptors, conivaptan decreases water reabsorption in the collecting duct of the kidney, leading to increased urine output and correction of hyponatremia. This dual mechanism of action is responsible for conivaptan's efficacy in treating euvolemic and hypervolemic hyponatremia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe conivaptan's mechanism of action.
**Option B:** This option is incorrect because it is not specific to conivaptan and could apply to other vasopressin receptor antagonists.

**Clinical Pearl / High-Yield Fact**
Conivaptan is the first non-selective vasopressin receptor antagonist approved for the treatment of euvolemic and hypervolemic hyponatremia. Its unique dual action on V1A and V2 receptors makes it an effective treatment option for patients with hyponatremia.

**Correct Answer:** C.