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: Pediatrics
[{'content': 'What is the cardiothoracic ratio in children is - \nSelect and explain. \nA. 30-35%, B. 40-45%, C. 50-55%, D. 60-65%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: “The cardiac silhouette occupies 50-55% of the chest width.\nCardiomegaly is present when the cardiothoracic (CT) ratio is more than 55%”\xa0he CTR is measured on a PA chest x-ray and is the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs / edge of pleura).\nA normal measurement should be <0.5(50%).', 'role': 'assistant'}]