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': 'pH of freshly mixed MTA is: \nSelect and explain. \nA. 7.2, B. 10.2, C. 11, D. 12', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Mineral trioxide aggregate (MTA) is composed of tricalcium silicate, tricalcium aluminate, tricalcium oxide and silicate oxide.\n\nBismuth oxide is added to the mixture for radiopacity.\npH - 12.5 (when set).\npH of freshly mixed MTA is 10.\nSetting time is 2 hours 45 minutes.\nCompressive strength—40 MPa (immediately after setting) which increases to 70 MPa after 21 days.', 'role': 'assistant'}]