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
Retinoblastoma is bilateral in: 
Select and explain. 
A. 1% of cases, B. 50% of cases, C. 100% of cases, D. 30% of cases
D: 30% of cases
Answer: D: 30% of cases 
Explanation: Ans. 30% of cases