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
Cause of oligohydramnios is: 
Select and explain. 
A. Oesophageal atresia, B. Duodenal atresia, C. Rena! agenesis, D. Diabetes
C: Rena! agenesis
Answer: C: Rena! agenesis 
Explanation: Rena! agenesis