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': 'Endotoxins differ from exotoxins in that endotoxins \nSelect and explain. \nA. are proteins, B. are heat labile, C. are highly antigenic, D. activate complement by the alternate pathway', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]