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
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 - 
Select and explain. 
A. Primary hypothyroidism, B. Cong. adrenal hyperplasia, C. Panhypopituitarism, D. Pyloric stenosis
B: Cong. adrenal hyperplasia
Answer: B: Cong. adrenal hyperplasia 
Explanation: None