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
[{'content': "Nagler's  reaction is an type of \nSelect and explain. \nA. Neutralization reaction, B. Complement fixation test, C. Agglutination test, D. Precipitation reaction", 'role': 'user'}, {'content': "Answer: A \nExplanation: Cl. perfringens is grown on a medium containing 6% agar, 5% Fildes' peptic digest of sheep blood and 20% human serum or 5% egg yolk in a plate.\xa0\nNeomycin sulphate may be added to the medium to make it more selective by inhibiting aerobic spore bearers and coliforms.\xa0\nTo one half of the plate, antitoxin is spread on the surface.\xa0\nThe inoculated culture plate is incubated at 37°C for 24 hours.\xa0\nColonies on the half plate without the antitoxin will be surrounded by opacity while colonies on the other half with antitoxin shows no opacity, due to specific neutralization of the alpha toxin.\nAlpha toxin (lecithinase C) splits lecithin into phosphoryl choline and a diglyceride (lipid).\xa0\nThe lipid deposits around the colonies resulting in opacity.\n\nRef : textbook of microbiology, C P Baveja 5th edition pg no:228", 'role': 'assistant'}]