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: Forensic Medicine
[{'content': 'Faint letter mark can be made visible by : \nSelect and explain. \nA. Infrared photography, B. Spectrophotometer, C. Ordinary light, D. X-ray', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Infrared photography', 'role': 'assistant'}]