Which of the following viral families is known to be causally associated with tumor formation in healthy appearing human adults?

A Papovavirus is any member of the former virus family of Papovaviridae. They are mainly associated with various neoplasms in mammals. The family of Papovaviridae is no longer used in recent taxonomy, but is split into the Papillomaviridae and the Polyomaviridae. HPV is a member of the Papillomaviridae family and is causally associated with cervical cancer in otherwise healthy individuals Hepatitis C virus is a member of the flaviviruses family and causes chronic hepatitis and in severe cases is a factor in liver cancer development Paramyxoviruses include agents such as respiratory syncytial virus and measles virus and are not associated with carcinomas Human polyoma viruses include BK and JC viruses, which have been associated with immunocompromised patients, and their role in formation of human tumors is still under investigation. Ref: Ray C.G., Ryan K.J. (2010). Chapter 19. Papilloma and Polyoma Viruses. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.