This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Human Immunodeficiency Virus, Subject name: Microbiology
Most common oncogenic RNA virus: 
Select and explain. 
A. Retrovirus, B. Picornavirus, C. Orthomyxovirus, D. Paramyxovirus
A: Retrovirus
Answer: A: Retrovirus 
Explanation: Ans. is 'a' i.e., Retrovirus (Ref: Ananthanarayan, 9th/e, p. 565 and 8th/e, p. 563, 565)Retroviruses contain an RNA genome and an RNA-directed DNA polymerase (reverse transcriptase). Both HIV and HTLV are oncogenic retrovirus.