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: Ophthalmology
A 2- year old child presented with leucocoria in the right eye since 2 months. On examination a total retinal detachment was present in the same eye. Ultrasound B scan revealed a heterogenous subretinal mass with calcification. The most likely clinical diagnosis is: 
Select and explain. 
A. Coats- disease, B. Retinoblastoma, C. Toxocariasis, D. Retinal tuberculoma
B: Retinoblastoma
Answer: B: Retinoblastoma 
Explanation: B i.e. Retinoblastoma Leukokoria in a child less than 6 years with hetrogenous mass & calcification on USG or CT scan is diagnostic of retinoblastomaQ. It may lead to secondary glaucoma & retinal detachment.