<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 41-year-old woman comes to the physician because of a 1-year history of fatigue, irregular menstrual cycles, and recurrent sinus infections. Examination shows hirsutism and hypopigmented linear striations on the abdomen. Serum studies show hypernatremia, hypokalemia, and metabolic alkalosis. A 24-hour urinary cortisol level is elevated. Serum ACTH is also elevated. High-dose dexamethasone does not suppress serum cortisol levels. Which of the following is the most likely underlying cause of this patients condition?? A: Adrenal carcinoma, B: Adrenal adenoma, C: Pituitary adenoma, D: Pheochromocytoma, E: Small cell lung cancer,  <response>: This is a clinical vignette describing a patient with signs and symptoms of Cushings syndrome, such as fatigue, irregular menses, hirsutism, striae, hypokalemia, alkalosis, and elevated 24-hour urinary cortisol. The key finding is that high-dose dexamethasone fails to suppress serum cortisol levels, indicating adrenal autonomy or ectopic ACTH production rather than a pituitary tumor. The elevated ACTH level rules out an adrenal tumor, pointing to an ectopic source of ACTH as the most likely diagnosis.E: Small cell lung cancer 