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
A 25-year-old male presents with weakness, occasional vomiting hypotension, skin and mucous membrane pigmentation. The diagnosis can be best established by - 
Select and explain. 
A. Metyrapone test, B. Basal plasma cortisol levle, C. 24- hour urinary 17-Ketosteroid, D. ACTH stimulation test
D: ACTH stimulation test
Answer: D: ACTH stimulation test 
Explanation: None