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: Dental
[{'content': 'Pulpal pain is most intense in \nSelect and explain. \nA. Acute closed pulpitis, B. Acute open pulpitis, C. Pulp hyperaemia, D. Pulp necrosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]