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
Dihydroergotamine differs from ergotamine in the following respect : 
Select and explain. 
A. 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
D: It is more potent α-adrenergic blocker and less potent vasoconstrictor
Answer: D: It is more potent α-adrenergic blocker and less potent vasoconstrictor 
Explanation: Hydrogenation of ergot alkaloids decrease their vasoconstrictor action and increase the α-blocking activity.