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: Dental
[{'content': 'The organism least resistant to thermal inactivation is \nSelect and explain. \nA. bacterial spores., B. virus., C. Streptococcus mutans., D. spirochete.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]