This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunity, Subject name: Pathology
[{'content': 'Preformed antibodies cause: \nSelect and explain. \nA. Hyperacute rejection, B. Acute rejection, C. Chronic rejection, D. Acute humoral rejection', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Hyperacute rejection(Ref: R 9th/pg 231-234)Hyperacute rejection occurs when preformed antidonor antibodies are present in the circulation of the recipient even prior to transplantation.', 'role': 'assistant'}]