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': 'One unit of diphtheria antitoxin was defined as the smallest amount of antitoxin required to neutralise ? \nSelect and explain. \nA. 100 MLD of toxin, B. 200 MLD of toxin, C. 300 MLD of toxin, D. 400 MLD of toxin', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 100 MLD of toxin . Minimum lethal dose (MLD) of the diphtheria toxin is defined as the least amount of the toxin required to kill a guinea pig weighing 250 gm within 96 hours after subcutaneous inoculation. . One unit of antitoxin was defined as the smallest amount of antitoxin required to neutralize 100 MLD of toxin.", 'role': 'assistant'}]