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
Function of Ig A is - 
Select and explain. 
A. Acts as a mucosal barrier for infection, B. Circulating antibody, C. Kills virus infected cells, D. Activates macrophages
A: Acts as a mucosal barrier for infection
Answer: A: Acts as a mucosal barrier for infection 
Explanation: Question repeated