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
Follow is the marker of HIV infection in blood - 
Select and explain. 
A. Reverse Transcriptase, B. DNA polymerase, C. RNA polymerase, D. None
A: Reverse Transcriptase
Answer: A: Reverse Transcriptase 
Explanation: viral replicatin(indicate infectivity) detected by demonstration of reverse transcriptase REF:MICROBIOLOGY ANANTHA NARAYANAN NINTH EDITION PAGE.578