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
Exchange of trace evidence occurs, when a person comes in contact with other person. This principle is called: 
Select and explain. 
A. Locard's principle, B. Quetelet's rule, C. Petty's principle, D. None of the above
A: Locard's principle
Answer: A: Locard's principle 
Explanation: 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.