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: Gynaecology & Obstetrics
Most useful investigation for VVF is: 
Select and explain. 
A. Three swab test, B. Cystoscopy, C. Urine culture, D. IVP
B: Cystoscopy
Answer: B: Cystoscopy 
Explanation: The most useful investigation in case of VVF is cystoscopy as it helps to confirm the size, position and number of fistulas.