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
Which of the following is the commonest site of ectopic pregnancy? 
Select and explain. 
A. Isthmus, B. Ampulla, C. Intestitial, D. Infundibulum
B: Ampulla
Answer: B: Ampulla 
Explanation: The frequency of location of tubal ectopic pregnancy are : 55% in ampulla, 25% in isthmus, 18% in infundibulum and 2% in the interstitial segment of fallopian tube. Ref: Textbook of Obstetrics By D C Dutta, 6e page 179.