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
Which of the following statements is true about isotypic variation ? 
Select and explain. 
A. These result due to subtle amino acid changes resulting from allelic differences, B. These result due to changes in amino acid in heavy and light chain at variable region, C. Changes in heavy and light chain in constant region is responsible for class and subclass of immunoglobulins, D. These are areas in antigen that bind specifically to antibody
C: Changes in heavy and light chain in constant region is responsible for class and subclass of immunoglobulins
Answer: C: Changes in heavy and light chain in constant region is responsible for class and subclass of immunoglobulins 
Explanation: None