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: Medicine
[{'content': 'After effective cardiopulmonary resuscitation there is: \nSelect and explain. \nA. Constriction of pupil, B. Dilation of pupil, C. Elevation of BP, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]