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': "Direct coomb's test detects - \nSelect and explain. \nA. Antigen in serum, B. Antibodies in RBC surface, C. Antigen in RBC surface, D. Antibodies in serum", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]