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: Pharmacology
Which of the following antihypertensive agents in most likely to cause an exaggerated response to an injected catecholamine? 
Select and explain. 
A. Propranolol, B. Hydralazine, C. A thiazide diuretic, D. Gauanethidine
D: Gauanethidine
Answer: D: Gauanethidine 
Explanation: None