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: Pathology
[{'content': 'Most commonly submerged tooth is \nSelect and explain. \nA. Mand. primary 1st molar, B. Mand. primary 2nd molar, C. Maxi. primary 1st molar, D. Maxi. primary 2nd molar', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]