This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and Health, Subject name: Social & Preventive Medicine
True about Chick-Martin test - 
Select and explain. 
A. Phenol is taken as standard, B. Test for efficacy of disinfectant, C. Disinfection in presence of organic matter, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. is 'd' i.e., All of the above o There is no reliable test available to determine the efficacy of a disinfectant,o This is due to the number of parameters which influence disinfectant activity,o Traditionally in such tests phenol is taken as the standard,o Two important tests areRideal-Walker testSuspensions containing equal numbers of typhoid bacilli are submitted to action of varying concentration of phenol and of the disinfectant to be tested.The dilution of test disinfectant which sterilises the suspension in given time, divided by the corresponding dilution of phenol, is stated as the phenol coefficient of disinfectant (phenol-1).In this test disinfectant react directly without any organic matter being present.Chick-Martin testIn this, the disinfectant acts in the presence of organic matter (dried yeast or feces).