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: Surgery
Cause of atonic bladder is: 
Select and explain. 
A. Injury to sacral plexus, B. Injury to upper thoracic cord, C. Pregnancy, D. UTI
A: Injury to sacral plexus
Answer: A: Injury to sacral plexus 
Explanation: A i.e. Injury to sacral plexus