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': 'What is the approximate stress caused by polymerisation shrinkage of composite? \nSelect and explain. \nA. 1 Mpa, B. 5 Mpa, C. 15 Mpa, D. 30 Mpa', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]