This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
A 6–month old boy weighing 3.2 kg presents with recurrent vomiting and polyuria. Investigations show blood area 60 mg/dl creatinine 0.7 mg/dL, calcium 12.8 mg/dL, phosphate 3 mg/dL, pH 7.45, bicarbonate 25 mEq/L and PTH 140 pg ml (normal <60 pg/ml). Daily urinary calcium excretion is reduced. Ultrasound abdomen show bilateral nephrocalcinosis. The most likely diagnosis is – 
Select and explain. 
A. Bartter syndrome, B. Mutation of the calcium sensing receptor, C. Ps eudo–ps eudohypoparathyroidism, D. Parathyroid adenoma
B: Mutation of the calcium sensing receptor
Answer: B: Mutation of the calcium sensing receptor 
Explanation: None