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
All except one is true regarding fallopian tube 
Select and explain. 
A. Fertilization occurs in ampullary portion of fallopian tube, B. There are no longitudinal muscle fibres in interstitial portion of tube, C. It has 2 sources of blood supply, D. Isthmus in narrower portion of fallopian tube.
D: Isthmus in narrower portion of fallopian tube.
Answer: D: Isthmus in narrower portion of fallopian tube. 
Explanation: Interstitium is narrowest portion of fallopian tube.