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
The major constituents in agar are 
Select and explain. 
A. Fats, B. Aminoacids, C. Polysaccharides, D. Polypeptides
C: Polysaccharides
Answer: C: Polysaccharides 
Explanation: Agar, a polysaccharide extract of a marine alga, is uniquely suitable for microbial cultivation because it is resistant to microbial action and becauseit dissolves at 100degC but does not gel until cooled below 45degC; cells can be suspended in the medium at 45degC and the medium quickly cooled to a gel without harming them.Ref: Jawetz, Melnick, & Adelberg's Medical Microbiology; Twenty-Seventh Edition; Chapter 5; Cultivation of Microorganisms