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': 'Biological indicator for determining efficacy of autoclaving is: September 2009 \nSelect and explain. \nA. Pseudomonas aeruginosa, B. Clostridium Perfringenes, C. Bacillus stearothermophilus, D. Salmonella typhi', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Bacillus stearothermophilus', 'role': 'assistant'}]