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: Radiology
[{'content': 'The overall hea size in tetralogy of Fallot is usually: \nSelect and explain. \nA. Markedly enlarged, B. Normal or relatively small, C. Slightly enlarged, D. Moderately enlarged', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Normal or relatively small', 'role': 'assistant'}]