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': "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\xa0\n\nIt States that " When two objects come into contact with each other, there is always transfer of some material between them".\nThis is helpful in crime investigations, especially in sexual offences.', 'role': 'assistant'}]