This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Which among the following body secretions does NOT contain ABO antigens? \nSelect and explain. \nA. CSF, B. Plasma, C. Saliva, D. Semen', 'role': 'user'}, {'content': "Answer: A \nExplanation: The ABO(H) antigens are found not only on red cells, but also on other blood cells, in most body fluids such as saliva, gastric juice, semen, plasma and sweat (except cerebrospinal fluid), and on the cell membranes of tissues such as intestine, urothelium, and vascular endothelium. Ref: Wintrobe's clinical hematology, edited by John P. Greer, M.d., Volume 1, 2009, Page 636.", 'role': 'assistant'}]