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
An example of covalent drug receptor interaction: 
Select and explain. 
A. Noradrenaline binding to β1  adrenergic receptor, B. Acetylcholine binding to muscarinic receptor, C. Prazosin binding to α1   adrenergic receptor, D. Phenoxybenzamine binding to alpha adrenergic receptor
D: Phenoxybenzamine binding to alpha adrenergic receptor
Answer: D: Phenoxybenzamine binding to alpha adrenergic receptor 
Explanation: Phenoxybenamine is an irreversible (covalent) antagonist at alpha receptors. All other drugs mentioned are reversibly interacting with their receptors.