This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hemolytic anemia, Subject name: Pediatrics
[{'content': "Direct Coomb's test is positive in hemolytic anemia due to: \nSelect and explain. \nA. Paraxysmal cold hemoglobinuria, B. Paroxysmal nocturnal hemoglobinuria, C. Idiopathic thrombocytopenic purpura, D. Hemolytic uremic syndrome", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Paroxysmal cold hemoglobinuria: Caused by the presence of cold-reacting autoantibodies (anti-P Ab) in the blood - Hence, Direct coombs test is positive. Characterized by the sudden presence of hemoglobinuria, typically after exposure to cold temperatures.', 'role': 'assistant'}]