This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Microbiology Pa 1 (History, Microscopy, Stains and Structure and Physiology of Bacteria), Subject name: Microbiology
[{'content': 'Robe Koch assistant advised him to use agar instead of gelatin for solidifying culture media for cultivation of bacteria because \nSelect and explain. \nA. Agar has more nutrients, B. Gelatin melts at 37oC, C. Gelatin is not easily available, D. Agar is cheaper', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Gelatin was the substance originally used to gel culture media. However, gelatin is liquid at 35oC., the optimum temperature for many bacteria. In addition, some bacteria are capable of liquifying the gelatin, making it an unsuitable solidifying agent. Agar has neither of these drawbacks. Agar is preferred over gelatin, as it is bacteriologically ine, melts at 98degC and usually solidifies at 42degC.', 'role': 'assistant'}]