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
[{'content': 'A 1–month old baby present with frequent vomiting and failure to thrive. There are features of moderate dehydration. Blood sodium in 122 mEq/1 and potassium is 6.1 mEq/1. The most likely diagnosis is – \nSelect and explain. \nA. Gitelman syndrome, B. Bartter syndrome, C. 21–hydroxylase deficiency, D. 11–β hydroxylase deficiency', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Blood parameters indicate Hyponatremia and Hyperkalemia in this patient. All conditions other than 21 hydroxylase deficiency present with Hypokalemia.', 'role': 'assistant'}]