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
Tumor involves inferior Venacava, what is the staging of Wilms tumour ? 
Select and explain. 
A. Stage II a, B. Stage III b, C. Stage III, D. Stage IV
C: Stage III
Answer: C: Stage III 
Explanation: Tumour extension to inferior Venacava occurs in Stage III of Wilms tumour.