This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Physiology
During peristalsis which of the following is not involved? 
Select and explain. 
A. NO, B. Substance P, C. Noradrenalin, D. VIP
C: Noradrenalin
Answer: C: Noradrenalin 
Explanation: Ach & Substance P are responsible for the proximal contracting segment of peristalsis NO & VIP are responsible for the distal Relaxation Ref: Ganong 25th ed/page 497