This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Human identification, Subject name: Forensic Medicine
[{'content': "Exchange of trace evidence occurs, when a person comes in contact with other person. This principle is called: \nSelect and explain. \nA. Locard's principle, B. Quetelet's rule, C. Petty's principle, D. None of the above", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Locard\'s Principle of Exchange: It states that "When two objects come into contact with each other, there is always transfer of some material between them" This is helpful in crime investigations, especially in sexual offences.', 'role': 'assistant'}]