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: Gynaecology & Obstetrics
[{'content': 'Red degeneration most commonly occurs at : \nSelect and explain. \nA. 1st trimester, B. Second trimester of pregnancy, C. Third trimester of pregnancy, D. Puerperium', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Second trimester of pregnancy', 'role': 'assistant'}]