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
Semen stains on clothes can be identified by: 
Select and explain. 
A. Infrared rays, B. Magnifying lens, C. Spectrometry, D. Ultraviolet rays
D: Ultraviolet rays
Answer: D: Ultraviolet rays 
Explanation: Ultraviolet rays