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: Biochemistry
Isomer differences of position of -H and -OH at 2", 3', and 4' carbon atom of glucose are called? 
Select and explain. 
A. Optical isomers, B. Epimers, C. Anomers, D. D,L isomers
B: Epimers
Answer: B: Epimers 
Explanation: Ans. is 'b' i.e., Epimers Isomers differing as a result of variations in configuration of the -OH and -H on carbon atoms 2, 3, and 4 of glucose are known as epimers. Biologically, the most impoant epimers of glucose are mannose and galactose, formed by epimerization at carbons 2 and 4, respectively