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': 'Which of the following is used as an indicator for plasma sterilization? \nSelect and explain. \nA. Bacillus subtilis, B. Bacillus stearothermophilus, C. Bacillus pumilus, D. Clostridium tetani', 'role': 'user'}, {'content': 'Answer: B \nExplanation: For determining the efficacy of moist heat sterilization, spores of Bacillus stearothermophilus are used as the test organism. This is a thermophilic organism with an optimum growth temperature of 55-60oC and its spores require an exposure of 12 minutes at 121oC to be killed. Ref: Textbook of Microbiology by Ananthanarayan, 8th edition, Page 32; 6th edition, Page 27.', 'role': 'assistant'}]