Infectious mononucleosis is caused by?
(A) EBV (B) CMV (C) HIV (D) HSV
(A) Epstein-Barr virus (EBV) infections (or HHV-4) is causative for following infections:

Infectious mononucleosis
Nasopharyngeal carcinoma
Burkiu's lymphoma
Oral hairy leukoplakia
Post-transplant lymphoproliferative diseases