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: Microbiology
[{'content': 'In contact dermatitis which cells play major role \nSelect and explain. \nA. T- cells, B. B-cells, C. Langhans cells, D. Macrophage', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]