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
A two-year old boy presented with episodes of becoming dusky. On examination, there was central cyanosis and clubbing. There was no pallor, oedema or respiratory distress. The hea was normal sized with a parasternal heave. A systolic thrill was palpable over the left middle sternal border. First hea sound was normal and only the aoic component was audible in the second hea sound. Liver was not enlarged - What would be the likely diagnosis ? 
Select and explain. 
A. Congenital methemoglobinemia, B. Eisenmenger syndrome, C. Aoic stenosis, D. Tetralogy of Fallot
D: Tetralogy of Fallot
Answer: D: Tetralogy of Fallot 
Explanation: Ans. is 'd' i.e., Tetralogy of fallot o Features in this child suggestive of TOF : - i) Cyanosis at 2 year (not at bih) ii) No pallor, dysnea or edema No CHF iii) Normal sized hea o These features suggest the diagnosis of TOF. o These have been explained earlier.