This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Surgery
Which of the following is least useful in Rx of "Overactive bladder"? 
Select and explain. 
A. Oxybutynin, B. Tolterodine, C. Duloxetine, D. Darifenacin
C: Duloxetine
Answer: C: Duloxetine 
Explanation: Duloxitin is use in the treatment of stress incontinence.