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: Pharmacology
FK 506 is a type of : 
Select and explain. 
A. Immunoglobulin antibody, B. Non-depolarizing muscle relaxant, C. Macrolide antibiotic, D. Opioid anaesthetic
C: Macrolide antibiotic
Answer: C: Macrolide antibiotic 
Explanation: Tacrolimus is also known as FK-506. It is an immunosuppressant macrolide antibiotic produced by Streptomyces tsukubaensis.
Muromonab CD3 is also known as OKT3. It is a monoclonal antibody against CD3 cells.