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: Unknown
[{'content': 'The only reliable means of diagnosing acute cardiac rejection before substantial myocardial damage has occurred is \nSelect and explain. \nA. Echocardiography, B. ECG, C. Endomyocardial biopsy, D. Ultrasound', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Of the major complications, allograft rejection is the primary problem requiring surveillance; scheduled endomyocardial biopsy is the only reliable means of diagnosing acute cardiac rejection before substantial myocardial damage has occurred and at a stage that is reversible in the majority of instances. Rejection is characterized by interstitial lymphocytic inflammation that, in its more advanced stages, damages adjacent myocytes; the histology resembles myocarditis. When myocardial injury is not extensive, the “rejection episode” is usually either self-limited or successfully reversed by increased immunosuppressive therapy. Advanced rejection may be irreversible and fatal if it is not promptly treated.', 'role': 'assistant'}]