This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Number of variable regions on each light and heavy chain of an antibody - 
Select and explain. 
A. 1, B. 2, C. 3, D. 4
A: 1
Answer: A: 1 
Explanation: A light chain has two successive domains: one constant domain and one variable domain. Heavy chain with one variable (VH) domain followed by a constant domain (CH) Ref: Ananthanarayan & Panikers textbook of microbiology 9th edition pg:94