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
After an endoscopy a technician kept the instrument for sterilization. Which of the following agent is used for sterilization of fibre optic instruments? 
Select and explain. 
A. Glutaraldehyde, B. Chlorine, C. Autoclave, D. Phenol
A: Glutaraldehyde
Answer: A: Glutaraldehyde 
Explanation: Glutaraldehyde, which has two reactive aldehyde groups, is 10 times more effective than formaldehyde and is less toxic. It denatures proteins and nucleic acids. Both proteins and nucleic acids contain essential -NH2 and -OH groups, which are the main sites of alkylation. In hospitals, it is used to sterilize respiratory therapy equipment, endoscopes, and hemodialysis equipment. Ref: Levinson W. (2012). Chapter 13. Sterilization & Disinfection. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.