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': 'Stalactite growth in ghee broth is due to \nSelect and explain. \nA. H. influenza, B. C. diphtheria, C. Y -pestis, D. T. pallidium', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Y. pestis Culture characteristic -Growth occurs over a wide range of temperature (range 2-45degC) and pH (5-9.6 optimum 7.2). The optimum temperature for growth is 27degC (unlike most pathogens). - In ghee broth a characteristic growth occurs which hangs down into broth from the surface resembling stalactites - Stalactite growth. - On blood agar colonies are dark due to the hemin pigment.", 'role': 'assistant'}]