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': "Gram-negative bacteria doesn't take gram stain because it is made of: \nSelect and explain. \nA. Polysaccharide, B. Lipopolysaccharide, C. Techoic acid, D. None of the above", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. d. None of the above', 'role': 'assistant'}]