21. Which of the following viruses causes chickenpox?
a) Herpes simplex virus
b) Varicella-zoster virus
c) Human immunodeficiency virus (HIV)
d) Hepatitis B virus
22. The immune response mediated by antibodies is most effective against which type of viral infection?
a) Extracellular viruses
b) Intracellular viruses
c) DNA viruses
d) Retroviruses
23. The viral enzyme responsible for reverse transcription in retroviruses is called:
a) Reverse transcriptase
b) RNA polymerase
c) DNA polymerase
d) Ligase
24. Which of the following viruses is responsible for causing infectious mononucleosis?
a) Epstein-Barr virus
b) Influenza virus
c) Human immunodeficiency virus (HIV)
d) Hepatitis C virus
25. The process of a virus integrating its DNA into the host genome is characteristic of which type of virus?
a) DNA virus
b) RNA virus
c) Retrovirus
d) Papillomavirus
