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: Microbiology
Cold sterilization is ? 
Select and explain. 
A. Ionizing radiation, B. Mechanical filtration, C. Ultrasonic, D. Sonic vibrations, heating, then sudden cooling
A: Ionizing radiation
Answer: A: Ionizing radiation 
Explanation: Ans. is 'a' i.e., Ionizing radiation