Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[Q]: Gastro-esophageal sphincter sphincter is located at the stomach end of the esophagus and opens to allow the bolus to enter the stomach.
[A]: Which sphincter is located at the stomach end of the esophagus and opens to allow the bolus to enter the stomach?


[Q]: Mucous does the esophagus produce for lubrication.
[A]: What does the esophagus produce for lubrication?


[Q]: Ammonia (nh3) is one of the few thermodynamically stable binary compounds of nitrogen with a nonmetal.
[A]:
What (nh3) is one of the few thermodynamically stable binary compounds of nitrogen with a nonmetal?