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
Incidence of preterm delivery in twin pregnancy is: 
Select and explain. 
A. 25%, B. 50%, C. 75%, D. 100%
B: 50%
Answer: B: 50% 
Explanation: 50%