This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunomodulators, Subject name: Pharmacology
[{'content': 'Mechanism of action of Rituximab? \nSelect and explain. \nA. Targets CD 20 antigen, B. Targets CD 52 antigen, C. Targets CD 22 antigen, D. Targets CD 38 antigen', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Rituximab acts on CD 20 B cell antigen and useful in Hodgkins lymphomaRef: Sharma and Sharma 3rd ed/pg 874', 'role': 'assistant'}]