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
Spore of which bacteria is used as sterilization control of Plasma sterilization: 
Select and explain. 
A. B. subtilis, B. B. pumilis, C. Cl. tetani, D. B. stearothermophilus
D: B. stearothermophilus
Answer: D: B. stearothermophilus 
Explanation: Biological Sterilization Indicator of plasma sterilization: B. stearothermophillus, B. subtilis subspecies niger