Oncogene was first identified in: (A) Epstein-Barr Virus, (B) Echovirus, (C) Adenovirus, (D) Retrovirus
Answer is D. (D) Retrovirus > Cellular Protooncogenes were first discovered in their mutated or "oncogenic" forms as "passengers" within the genome of acute transforming retroviruses by the 1989 Nobel laureates Harold Varmus and Michael Bishop.