In a chronic smoker with mild haemoptysis.He also gave a history of hypertension and obesity.Lab data showed raised ACTH levels,which were not suppressed by dexamethasone.The cause for the Cushing's syndrome in the patient is:

• A. MEN I
• B. Pituitary adenoma
• C. Adrenal cortical adenoma
• D. Ectopic ACTH secreting tumor