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': 'Tolazoline is used as: \nSelect and explain. \nA. A thrombin inhibitor in peripheral angiography, B. A vasodilator in treating coronary artery stenosis during angio procedures, C. A vasoconstrictor in treatment of varices, D. An antispasmodic during biliary spasm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]