<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 16-year-old male presents to his pediatrician with a sore throat. He reports a severely painful throat preceded by several days of malaise and fatigue. He has a history of seasonal allergies and asthma. The patient is a high school student and is on the school wrestling team. He takes cetirizine and albuterol. His temperature is 100.9F 38.3C, blood pressure is 10070 mmHg, pulse is 100min, and respirations are 20min. Physical examination reveals splenomegaly and posterior cervical lymphadenopathy. Laboratory analysis reveals the following:Serum:Na: 145 mEqLK: 4.0 mEqLCl-: 100 mEqLHCO3-: 24 mEqLBUN: 12 mgdLCa2: 10.2 mgdLMg2: 2.0 mEqLCreatinine: 1.0 mgdLGlucose: 77 mgdLHemoglobin: 17 gdLHematocrit: 47Mean corpuscular volume: 90 μm3Reticulocyte count: 1.0Platelet count: 250,000mm3Leukocyte count: 13,000mm3Neutrophil: 45Lymphocyte: 42Monocyte: 12Eosinophil: 1Basophil: 0Which of the following cell surface markers is bound by the pathogen responsible for this patients condition?? A: CD3, B: CD4, C: CD19, D: CD20, E: CD21,  <response>: Based on the patients symptoms of sore throat, malaise, fatigue, fever, lymphadenopathy, and splenomegaly, this appears to be a case of infectious mononucleosis caused by the Epstein-Barr virus EBV. The lymphocytosis and atypical lymphocytes on the CBC are also suggestive of this diagnosis. EBV infects and replicates in B lymphocytes, so the cell surface marker bound by EBV is CD21, which is expressed on B cells. CD3, CD4, and CD20 are found on T cells and CD19 is also found on B cells, but EBV specifically targets CD21.E: CD21 