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
Lalloo 50 yrs, a chronic smoker presents with a history of hemoptysis. He was having truncal obesity and hypertension. He had an elevated ACTH level which was not suppressible with high dose dexamethasone. What would be the most probable diagnosis - 
Select and explain. 
A. Bilateral adrenal hyperplasia, B. Adrenal adenoma, C. Pituitary tumor, D. Ectopic ACTH producing lung cancer
D: Ectopic ACTH producing lung cancer
Answer: D: Ectopic ACTH producing lung cancer 
Explanation: None