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
2 weeks old baby having scrotal pigmentation along with hyponatremia, gypoglycemia and hyperkalemia enzyme deficient? 
Select and explain. 
A. 11 beta hydroxylase, B. 21 a- hydroxylase, C. 3- Beta hydroxylase dehydrogenase, D. 17- hydroxylase deficiency
B: 21 a- hydroxylase
Answer: B: 21 a- hydroxylase 
Explanation: Ans. is 'b' i.e., 21 a- hydroxylase