This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
[{'content': 'Gram-positive bacteria stain during Gram staining \nSelect and explain. \nA. Blue, B. Red, C. Violet, D. Green', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan, and as a result are stained purple by crystal violet, whereas gram-negative bacteria have a thinner layer, so do not retain the purple stain and are counter-stained pink by safranin or carbol fuchsin. Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 13', 'role': 'assistant'}]