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: Pathology
Retinoblastoma spreads through? 
Select and explain. 
A. Vascular invasion, B. Direct invasion, C. Optic nerve, D. Lymphatic
C: Optic nerve
Answer: C: Optic nerve 
Explanation: None