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: Physiology
[{'content': 'Which of the following represents most dangerous situation: \nSelect and explain. \nA. Rh + ve mother, who is bearing 2nd Rh -ve child, B. Rh - ve mother, bearing her 2nd Rh + ve child, C. Rh + ye mother, bearing her 1st Rh -ve child, D. Rh — ye mover, bearing her 1st Rh + ye child', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]