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
[{'content': 'Dihydroergotamine differs from ergotamine in the following respect : \nSelect and explain. \nA. It is a more potent oxytocic, B. It has antiemetic property, C. It has high oral bioavailability, D. It is more potent α-adrenergic blocker and less potent vasoconstrictor', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Hydrogenation of ergot alkaloids decrease their vasoconstrictor action and increase the α-blocking activity.', 'role': 'assistant'}]