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
High level disinfectant is 
Select and explain. 
A. Isopropylalchol, B. Phenol, C. Benzalkonium chloride, D. Chlorine
D: Chlorine
Answer: D: Chlorine 
Explanation: Low – Level distinfectant – Benzalkonium chloride
Intermediate – Level distinfectant – Isopropylalchol,phenol
High – Level disinfectant – Gluteraldelyde, formaldehyde, H2O2, Chlorine