**Core Concept**
Verner-Morrison syndrome, also known as Vasoactive Intestinal Peptide (VIP)oma, is a rare endocrine disorder caused by a pancreatic or intestinal tumor that secretes excess vasoactive intestinal peptide (VIP). This leads to a constellation of symptoms due to the excessive action of VIP on various bodily systems.

**Why the Correct Answer is Right**
VIP exerts its effects primarily through the activation of adenylate cyclase in target tissues, leading to an increase in cyclic AMP (cAMP) levels. This results in vasodilation, increased intestinal secretion, and relaxation of smooth muscle. The symptoms of VIPoma include severe diarrhea, hypokalemia, weight loss, and dehydration, among others. The mechanism involves the inhibition of sodium absorption and chloride secretion in the intestine, leading to a significant loss of electrolytes and fluids.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while hypocalcemia can occur in VIPoma due to the binding of calcium to VIP, it is not a primary symptom.
**Option B:** Incorrect because while hyperglycemia can occur in VIPoma, it is not a direct result of VIP action.
**Option C:** Incorrect because while abdominal pain can occur in VIPoma, it is not a characteristic symptom.

**Clinical Pearl / High-Yield Fact**
VIPoma should be considered in the differential diagnosis of chronic diarrhea, particularly if it is severe and accompanied by significant electrolyte imbalances.

**Correct Answer: D.**