This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
[{'content': 'All of the following rabies vaccines are commercially available except - \nSelect and explain. \nA. Killed sheep brain vaccine, B. Human diploid cell vaccine, C. Vero continous cell vaccine, D. Recombinant glycoprotein', 'role': 'user'}, {'content': "Answer: D \nExplanation: Subunit vaccine -The glycoprotein subunit in the virus surface which is the protective antigen, has been cloned and recombinant vaccines produced. They are still in the experimental stage. REF:ANANTHANARAYAN AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO:536", 'role': 'assistant'}]