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
Robert Koch assistant advised him to use agar instead of gelatine for solidifying culture media for cultivation of bacteria as - 
Select and explain. 
A. Agar has more nutrition, B. Gelatin melts at 37°C, C. Gelatin is not easily available, D. Agar is cheaper
B: Gelatin melts at 37°C
Answer: B: Gelatin melts at 37°C 
Explanation: Agar is preferred to gelatin as a solidifying agent in culture media.
This is because gelatin melts at relatively low temperature (<35o C), while agar melts at around 85° C.
Therefore, when gelatin is incubated at the normal temperature for bacterial growth, i e. at 37° C, it melts, while agar remains solid.