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
What is the cardiothoracic ratio in children is - 
Select and explain. 
A. 30-35%, B. 40-45%, C. 50-55%, D. 60-65%
C: 50-55%
Answer: C: 50-55% 
Explanation: “The cardiac silhouette occupies 50-55% of the chest width.
Cardiomegaly is present when the cardiothoracic (CT) ratio is more than 55%” he 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).
A normal measurement should be <0.5(50%).