This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood, Subject name: Medicine
A 19-year-old college student develops a severe sore throat, cervical lymphadenopathy, and atypical lymphocytes on blood film. A heterophil antibody test is positive.For the above patient with a hematologic abnormality, select the most likely diagnosis. 
Select and explain. 
A. hyperthyroidism, B. rectal cancer, C. infectious mononucleosis, D. renal cell carcinoma
C: infectious mononucleosis
Answer: C: infectious mononucleosis 
Explanation: Heterophil antibodies react against sheep red cells and are not absorbed by the guinea pig kidney. They are positive in patients with infectious mononucleosis. In 90% of cases, liver enzymes are elevated. Examination of the blood film reveals a lymphocytosis with atypical lymphocytes.