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: Anatomy
Lower esophageal sphincter: 
Select and explain. 
A. Has no tonic activity, B. Has a tone which is provided by the sympathetic system, C. Relaxes on increasing abdominal pressure, D. Relaxes ahead of the peristaltic wave
D: Relaxes ahead of the peristaltic wave
Answer: D: Relaxes ahead of the peristaltic wave 
Explanation: D i.e. Relaxes ahead of the peristaltic wave