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: Medicine
[{'content': 'Newborn 7 days old with vomiting and dehydration clinical examination was normal except for by hyperpigmentation of nipple. Electrolytes Na: 120 meq.K: 9 meq. most likely diagnosis - \nSelect and explain. \nA. Primary hypothyroidism, B. Cong. adrenal hyperplasia, C. Panhypopituitarism, D. Pyloric stenosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]