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
Rideal - walker test is used to compare the efficiency of a disinfectant with that of phenol for the ability to kill 
Select and explain. 
A. S typhi, B. S paratyphi, C. Pseudomonas, D. E.coli
A: S typhi
Answer: A: S typhi 
Explanation: Rideal - walker test / phenol coefficient test - abilty to sterilize the suspension of S.typhi.