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: Medicine
All circulate in blood except- 
Select and explain. 
A. HBcAg, B. Anti HBC, C. HBeAg, D. HBsAg
A: HBcAg
Answer: A: HBcAg 
Explanation: None