Ans: A (QT prolongation) Ref: Harrison's Principles of Internal Medicine, 18ed.Explanation:Clinical Manifestations of HypocalcemiaPatients with hypocalcemia may be asymptomatic if the decreases in serum calcium are relatively mild and chronic.Moderate to severe hypocalcemia is associated with paresthesias, usually of the fingers, toes, and circumoral regions due to increased neuromuscular irritability.Chvostek's sign (twitching of the circumoral muscles in response to gentle tapping of the facial nerve just anterior to the ear) may be elicited.Carpal spasm may be induced by inflation of a blood pressure cuff to 20 mmHg above the patient's systolic blood pressure for 3 min (Trousseau's sign).Severe hypocalcemia can induce seizures, carpopedal spasm, bronchospasm. laryngo- spasm, andECG: Prolongation of the QT interval.Clinical Manifestations of HypercalcemiaMild hypercalcemia (up to 11-11.5 mg/dL)It is usually asymptomaticRecognized only on routine calcium measurements.Vague neuropsy chiatric symptoms, like trouble concentrating, personality changes, or depressionAssc with peptic ulcer disease or nephro-lithiasis, and increased fracture risk.More severe hypercalcemia (>12-13 mg/dL)CNS symptoms: Lethargy, stupor, or comaGastrointestinal symptoms (nausea, anorexia, constipation, or pancreatitis).Decreased renal concentrating ability, causing polyuria and polydipsia.Bone pain or pathologic fractures (in longstanding hyperparathyroidism).ECG changes: Bradycardia. AV block, and Short QT interval