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: Radiology
In Renal cell carcinoma investigation of choice to evaluate inferior venacava & renal vein for thrombus 
Select and explain. 
A. IVP, B. Coloured Doppler, C. USG, D. CT scan
B: Coloured Doppler
Answer: B: Coloured Doppler 
Explanation: B i.e. Coloured Doppler