This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Microbiology
The spores of which bacterium are used to check efficacy of hot air oven: 
Select and explain. 
A. Bacillus stearothermophilus, B. Bacillus atrophaeus, C. Bacillus subtilis, D. Bacillus cereus
C: Bacillus subtilis
Answer: C: Bacillus subtilis 
Explanation: Ans. C. Bacillus subtilisa. Spores of Bacillus subtilis are used as biological control in hot air oven sterilization.b. Spores of Bacillus atropheus are used as biological control in ETO sterilization.c. Spores of Bacillus pumilus are used as biological control of gamma sterilization.d. Spores and crystalline insecticidal proteins produced by B. thuringiensis have been used to control insect pests like mosquitoes.